Internal Medicine Journal 2001; 31: 53–59
`
`MEDICINE IN THE 21ST CENTURY
`
`Molecular medicine in the 21st century
`
`C. SEMSARIAN1 and C. E. SEIDMAN1,2
`
`1Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School and 2Brigham and Womens
`Hospital, Boston, Massachusetts, USA
`
`Abstract
`
`When Watson and Crick proposed the double helix
`model for DNA structure in a 2 page Nature article in
`1953, no one could have predicted the enormous
`impact this finding would have on the study of human
`disease. Over the last decade in particular, major
`advances have been made in our understanding of
`both normal biological processes and basic molecular
`mechanisms underlying a variety of medical diseases.
`Knowledge obtained from basic cellular, molecular
`and genetic studies has enabled the development of
`strategies for the modification, prevention and poten-
`tial cure of human diseases. This brief overview
`focuses on the enormous impact molecular studies
`have had on various aspects of medicine.The inherited
`cardiac disorder hypertrophic cardiomyopathy is used
`
`here as a model to illustrate how molecular studies
`have not only redefined ‘gold standards’ for diagnosis,
`but have also influenced management approaches,
`increased our understanding of fundamental disease-
`causing mechanisms and identified potential targets
`for therapeutic intervention. The near-completion of
`the Human Genome Project, which identifies the 3.2
`billion base pairs that comprise the human genome
`(the so-called ‘Book of Life’), has exponentially
`heightened the focus on the importance of molecular
`studies and how such studies will impact on various
`aspects of medicine in the 21st century. (Intern Med J
`2001; 31: 53–59)
`
`Key words: DNA, genetics, Human Genome
`Project, medicine, molecular.
`
`INTRODUCTION
`
`Over the last decade, major advances have been made
`in defining the molecular basis of many genetically
`transmitted medical diseases. Such advances have not
`only allowed us to gain a better understanding of the
`primary defect and basic molecular pathogenesis of
`disease, but have redefined the diagnostic ‘gold stan-
`dards’ of many disorders. Improved understanding of
`the molecular basis of disease will probably allow
`targeting of pharmacological strategies, as well as
`providing
`the cornerstone
`for gene
`therapy
`approaches.
`
`The recent announcement that the Human Genome
`Project has now sequenced over 90% of the 3.2 billion
`
`Correspondence to: Dr Christopher Semsarian, Department of Genetics,
`Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115,
`USA. Email: csemsar@genetics.med.harvard.edu
`Received 15 September 2000; accepted 17 October 2000.
`
`base pairs that comprise the human genome1 has
`heightened the focus and raised expectations of the
`impact that molecular studies will have on various
`aspects of medicine in the 21st century. Many new
`and exciting frontiers are opening in medicine, both
`to identify the thousands of genes in our genome and
`to understand their functions and interactions in
`human disease. It is therefore timely and appropriate
`to look briefly at how molecular studies affect the
`practice of medicine today, and what the future may
`hold.
`
`The field of cardiovascular medicine has been one of
`the leaders in demonstrating the importance of
`molecular studies in elucidating disease mechanisms,
`influencing clinical diagnosis and affecting manage-
`ment. Disease-causing gene defects have now been
`identified in several cardiovascular diseases, including
`cardiomyopathies, dysrhythmias, congenital heart
`malformations, vascular disorders and some forms of
`hypertension.2–6 Increasingly, molecular studies are
`
`00001
`
`EX1081
`
`

`

`54
`
`Semsarian & Seidman
`
`defining potential risk factors for atherosclerotic heart
`disease, giving insights that are informing gene
`therapy strategies for preventing coronary artery
`restenosis after angioplasty and promoting angiogen-
`esis in severe coronary artery disease.7–10
`
`Hypertrophic cardiomyopathy was the first of these
`cardiovascular diseases in which a genetic basis was
`identified and, as such, has acted as a paradigm for
`the study of a cardiovascular genetic disorder. Hyper-
`trophic cardiomyopathy will be used here as a model
`of how a genetic disorder is studied and how such
`studies have impacted on understanding disease
`mechanisms, identifying high risk subgroup popula-
`tions, clinical diagnosis and treatment.
`
`HYPERTROPHIC CARDIOMYOPATHY:
`A MODEL FOR THE STUDY OF AN
`INHERITED CARDIAC DISEASE
`
`Background
`Since the modern description of hypertrophic
`cardiomyopathy,11 much interest has been generated
`in this clinically diverse cardiac disorder. Hyper-
`trophic cardiomyopathy is a primary cardiac disorder
`characterized by hypertrophy, usually of the left
`ventricle, in the absence of other loading conditions
`such as aortic stenosis or hypertension.12 The disorder
`has a wide clinical spectrum, from a benign, asymp-
`tomatic course to symptoms of heart failure.13 The
`most serious complication is sudden cardiac death,
`with hypertrophic cardiomyopathy being
`the
`commonest cause of sudden cardiac death in individ-
`uals aged less than 35 years and in competitive
`athletes.14–17 Over the last 10 years, hypertrophic
`cardiomyopathy has been further defined as a ‘disease
`of the sarcomere’, with several disease-causing gene
`mutations being identified that encode sarcomeric
`proteins.2,18 Although previously thought of as a rare
`disorder, recent population-based studies suggest the
`prevalence of the condition to be as high as 0.2% (or
`one in 500) in the general population.19
`
`one-in-two risk of inheriting the mutation (gene
`defect).
`
`Since 1989, major advances have been made in
`understanding the molecular basis for hypertrophic
`cardiomyopathy. Hypertrophic cardiomyopathy is a
`genetically heterogeneous disease with several
`causative genes now identified. All of these genes
`encode sarcomere proteins and include the cardiac
`β-myosin heavy chain (β-MHC), cardiac troponin
`T gene, α-tropomyosin, myosin-binding protein
`C (MyBP-c), cardiac troponin I, essential and regula-
`tory myosin light chain and, more recently, titin and
`actin genes. A further form of hypertrophic cardiomy-
`opathy, co-inherited with the Wolff–Parkinson–White
`syndrome, has been localized to chromosome 7q3,
`but no gene has yet been identified.3,18,20
`
`The relative frequency of causative genes in hyper-
`trophic cardiomyopathy is summarized in Table 1.
`Over 100 mutations have now been identified in these
`genes, with most being of the missense type (i.e. a
`single base change resulting in an amino acid substi-
`tution). The identification of these sarcomere protein
`genes, coupled with basic functional studies, has shed
`new light on this disease both in understanding the
`underlying deficit and in clinical diagnosis and treat-
`ment.
`
`Impact of genetic studies on understanding pathogenesis
`
`The pathophysiology of hypertrophic cardiomyopathy
`is complex and this is reflected in the diversity of
`symptoms. These symptoms include chest pain, which
`may be typical of angina, symptoms related to
`pulmonary congestion (i.e. dyspnoea,
`fatigue,
`orthopnea and paroxysmal nocturnal dyspnoea),
`impaired consciousness (i.e. syncopal and presyncopal
`episodes) and palpitations. The precise mechanisms
`involved in these symptoms are not always clear in
`individual patients. However, some pathophysiological
`
`Table 1 Frequency of gene mutations in HCM
`
`Genetic basis of hypertrophic cardiomyopathy
`Hypertrophic cardiomyopathy was the first cardiovas-
`cular disorder for which the genetic basis was identified
`(genetic aetiologies for hypercholesterolaemia and
`Ehlers–Danlos syndrome, both potentially leading to a
`cardiac phenotype, preceded this). It is a heritable
`disorder that is transmitted as an autosomal dominant
`trait (i.e. affected individuals are heterozygous: they
`have one normal and one mutant copy of the gene).
`Offspring of affected individuals will therefore have a
`
`HCM gene
`β-Myosin heavy chain
`Cardiac myosin-binding protein C
`Troponin T
`α-Tropomyosin
`Troponin I
`Myosin light chains
`Actin
`Titin
`
`HCM, hypertrophic cardiomyopathy.
`
`Percentage of all HCM
`
`30–35%
`15–20%
`10–15%
`< 5%
`< 1%
`< 1%
`< 0.5%
`< 0.5%
`
`00002
`
`

`

`Molecular medicine: gene therapy
`
`55
`
`factors recognized to be associated with a clinical
`course involving such symptoms include left ventric-
`ular diastolic dysfunction, severe left ventricular
`outflow
`tract obstruction,
`impaired coronary
`vasodilator reserve and myocardial ischaemia and
`supraventricular/ventricular tachydysrhythmias.13,21
`
`tions that may be helpful in confirming the diagnosis
`or in establishing a ‘risk of sudden death’ profile
`include exercise testing (with or without echocardiog-
`raphy), ambulatory Holter monitoring, marked
`hypertrophy (>35 mm) and a history of cardiac
`events in other family members.13
`
`Identifying genes that cause hypertrophic cardiomy-
`opathy has allowed research to be directed to the key
`area of sarcomere function and how these mutations
`result in cardiac dysfunction. There are at least two
`potential ways in which the mutant genes could exert
`their dominant effect. A mutant sarcomere protein can
`act via a dominant negative mechanism, in which
`incorporation into the multimeric sarcomere structure
`disrupts function.The mutant protein acts as a ‘poison
`peptide’. Missense mutations that alter only a single
`amino acid of a contractile protein are likely to cause
`hypertrophic cardiomyopathy through this mecha-
`nism. Alternatively, a dominant mutation may
`functionally inactivate a gene, producing a null allele
`(non-functioning gene) and potentially reducing
`peptide concentrations by 50%. This situation,
`in
`which only one allele is operative, is also known as
`‘haploinsufficiency’. Studies expressing troponin T
`splice site hypertrophic cardiomyopathy mutations in a
`cultured avian myotube system have demonstrated the
`incorporation of mutated peptides into the sarcomere,
`accompanied by attenuated force development.22 Such
`data oppose the null allele hypothesis and imply that
`hypertrophic cardiomyopathy mutations produce their
`effects by a dominant negative mechanism.
`
`Impact of genetic studies on diagnosis
`
`the diagnosis of hypertrophic
`Until recently,
`cardiomyopathy largely involved electrocardiography
`and echocardiography. Clinical diagnosis can be made
`from the character of the pulse and left ventricular
`impulse and from the characteristic apical systolic
`murmur that increases with the Valsalva manoeuvre.
`There is often a fourth heart sound. The echocardio-
`gram is the investigation that most reliably confirms
`the diagnosis of hypertrophic cardiomyopathy and
`that provides detailed information about the distribu-
`tion and severity of hypertrophy, the left ventricular
`cavity size, assessment of left ventricular systolic and
`diastolic function,
`left ventricular outflow tract
`obstruction and mitral regurgitation. The electro-
`cardiogram has higher
`sensitivity
`than
`the
`echocardiogram in the detection of affected individ-
`uals in family studies, especially among children and
`adolescents, but has lower specificity when used for
`screening outpatient populations.23 Other investiga-
`
`With the advent of genetic screening, molecular diag-
`nosis has become the ‘gold standard’. Several
`important aspects of molecular diagnosis have
`evolved subsequently. Many individuals have been
`identified who carry the disease-causing mutation but
`who have not developed hypertrophy (genotype
`positive/phenotype negative). These individuals, who
`would previously have been classified as unaffected,
`can now have a diagnosis made in the absence of
`cardiac hypertrophy (preclinical diagnosis). While
`definition of such individuals has potential deleterious
`psychosocial implications, preclinical diagnosis allows
`potential treatment to be initiated early, with preven-
`tion of cardiac events a priority. Genetic diagnosis has
`also led to the recognition that particular gene muta-
`tions cause late-onset disease. For example, MyBP-c
`gene defects produce hypertrophy in the fourth and
`fifth decades of life, while β-MHC gene mutations
`cause hypertrophy by age 20 years in over 90% of
`individuals with these defects.24–26 Thus, the absence
`of hypertrophy does not exclude an individual in a
`family with known hypertrophic cardiomyopathy
`from carrying the gene defect.This has revolutionized
`screening protocols, which traditionally classified at-
`risk individuals over age 20 years without hypertrophy
`as unaffected. The findings from molecular diagnoses
`clearly indicate that, without genetic data, at-risk indi-
`viduals should be screened until at least age 40 years.
`
`A second, often overlooked, impact of molecular diag-
`nosis in hypertrophic cardiomyopathy has been the
`‘negative result’. By identifying a mutation in a family,
`one is now able to screen any individual within that
`family. This means that paediatric testing can pre-
`empt longitudinal clinical evaluations; if a child does
`not inherit the mutation (50% of the offspring of
`affected parents), the child need not be screened
`every 1–2 years and should be encouraged to partici-
`pate fully in routine school sporting activities and
`extracurricular athletics. Importantly, such informa-
`tion provides relief to parents from worrying for that
`child and the child’s offspring. It is pleasing to be able
`to tell an individual definitively that they do not carry
`the gene defect, rather than to say that their echo-
`cardiogram is normal at the moment but it will need
`to be checked again in 12 months.
`
`00003
`
`

`

`56
`
`Semsarian & Seidman
`
`Clearly, making a genetic diagnosis in a medical disease
`has numerous advantages. In hypertrophic cardiomy-
`opathy, a genetic diagnosis can also help in resolving
`ambiguous diagnoses, such as individuals with a border-
`line or modest increase in left ventricular wall thickness,
`including some trained athletes with hypertrophy,
`patients with systemic hypertension who are suspected
`of having hypertrophic cardiomyopathy, patients who
`have hypertrophy in less common sites (e.g. apical
`hypertrophic cardiomyopathy, where diagnosis can be
`difficult)27 and in children. Furthermore, one can now
`make antenatal diagnoses in families in which a
`mutation is known.While this clearly raises many ethical
`issues, prenatal diagnosis may be warranted in a family
`with a clearly documented ‘malignant’ phenotype.
`
`Current limitations in laboratory equipment avail-
`ability and the labour-intensive nature of this work
`mean that the greatest chance for an individual to
`have a genetic diagnosis is if they are part of a family
`with a history of the disease. This allows alternative
`genetic techniques, such as linkage analysis,
`to
`identify which gene is involved. Therefore, an impor-
`tant consideration in all inherited medical disorders is
`an accurate assessment by the clinician of the family
`history, which is considered to be the cornerstone of
`management of patients with genetic disease. Partic-
`ular emphasis should be placed on a history of the
`ages at death and causes of death, which may give
`some estimation of the risk of death within a specific
`family. Furthermore, because relatives of an affected
`individual have a risk that is several hundred times
`higher than the general population, clinical screening
`of such individuals is justified.
`
`Impact of genetic studies on treatment in hypertrophic
`cardiomyopathy
`
`Many treatment options are currently available for
`hypertrophic cardiomyopathy patients. This ranges
`from no treatment; use of pharmacological agents
`(e.g. calcium channel blockers, beta-blockers and
`diuretics); to dual chamber pacing, septal myotomy/
`myectomy and transeptal ablation of septal myo-
`cardium (i.e. the creation of a limited septal infarct by
`direct injection of alcohol into the septal perforator
`artery)28 for individuals with significant left ventric-
`ular outflow tract obstruction with symptoms
`unresponsive to drug therapy, for example.13
`
`Molecular studies have allowed significant advances to
`be made both in terms of targeting treatment and in
`identifying potential sites of intervention. There now
`appears to be a clear association of some mutations
`
`with severe disease (i.e. ‘malignant’ mutations). For
`example, the Arg719Trp or Arg403Gln mutations in
`the β-MHC gene have now been shown in several
`families worldwide to be associated with poor prog-
`nosis and early sudden death.24,25 Approximately 50%
`of individuals with these mutations die by age 40 years.
`This is in contrast to other mutations, for example
`MyBP-c mutations in which most have a normal life
`expectancy and minimal symptoms.26 Identification of
`such individuals with malignant mutations, who are
`therefore at high risk of sudden cardiac death, will
`enable clinicians to consider preventative measures.
`Currently,
`treatment options
`include
`long-term
`therapy with amiodarone or sotalol or an implantable
`cardioverter-defibrillator, the latter probably being the
`most definitive in hypertrophic cardiomyopathy
`patients at high risk of sudden death.29
`
`By understanding how sarcomere mutations perturb
`biophysical events of muscle contraction and cell
`signalling pathways within the myocyte, future inter-
`ventions may
`involve correcting such defects.
`Furthermore, with increased understanding of the
`genetic mechanisms, it may be possible to target
`therapy to mitigate the genetic defect or, conceivably,
`to correct the molecular abnormality; that is, to
`correct the single base abnormality in the mutant
`allele and effectively cure the disease. Alternatively,
`the dominant negative mechanism by which these
`gene mutations act has an impact on the potential for
`somatic gene therapy for hypertrophic cardiomy-
`opathy, which theoretically would have to be directed
`toward specific inactivation of the mutant allele.
`
`FROM GENE MUTATION TO
`CLINICAL DISEASE: UNRAVELLING
`THE MYSTERY
`
`In a disease such as hypertrophic cardiomyopathy, we
`now know of at least nine genes that are causative. We
`have some insight as to how mutations in these genes
`affect sarcomere function, but we know very little
`about how the dysfunctional sarcomere leads to the
`observed phenotype. Current and future efforts will
`focus on the signalling pathways that lead from the
`gene defect to disease and what factors influence this
`pathway to modify the end phenotype (Fig. 1).
`Recent interest has implied that a Ca2+–calcineurin
`pathway, shown to have a role in some forms of
`cardiac30,31 and skeletal muscle32 hypertrophy, may
`also be important in hypertrophic cardiomyopathy.
`However, emerging data suggest that this is not the
`case and other potential pathways are therefore the
`focus of intense study.33
`
`00004
`
`

`

`Molecular medicine: gene therapy
`
`57
`
`IMPACT OF THE HUMAN GENOME
`PROJECT ON MEDICINE
`
`When Watson and Crick first described their observa-
`tions regarding the double-helical structure of DNA
`in their 1953 Nature paper, they noted the structure’s
`‘novel features, which are of considerable biological
`interest’.42 What an understatement! Nearly 50 years
`later, one of the greatest of achievements was recently
`announced at a ceremony in the White House hosted
`by President Bill Clinton, the sequencing of the
`human genome, which spans some 3.2 billion base
`pairs.1,43 While the sequence is not totally complete or
`aligned, it is only a matter of months before it will be,
`when we will have the so-called ‘Book of Life’. The
`code will be useful and used as long as humans exist.
`With the world’s spotlight focused on the unravelling
`of the human genome, the question arises of how the
`human genome data will impact on current molecular
`studies and ultimately on the practice of medicine.
`
`By sequencing the human genome, thousands of
`genes have been and will be identified. Currently, at
`least 38 000 genes have been identified in the existing
`‘rough draft’ of the human genome sequence. The
`total remains a mystery, with many genome scientists
`predicting close to 50 000 genes.43,44 The outstanding
`issues directly resulting from this are: (i) the function
`of these genes, (ii) what defects in these genes can
`cause and (iii) how these genes interact. In most
`cases, such studies would involve both human and
`animal studies. There are currently many existing
`families with inherited disorders that span many areas
`of medicine (e.g. macular degeneration, diabetes,
`hearing loss, asthma and Alzheimer’s disease). Many
`studies of these inherited disorders have been
`impeded because of areas in the genome that were
`unknown. Human genome data will close such ‘gaps’
`and enable identification of novel genes that may or
`may not be disease causing. Animal studies, as well as
`in vitro/cellular studies, will also unravel many of the
`mysteries, with newly identified genes being knocked
`out or overexpressed, and subsequent analysis of the
`resulting phenotype giving preliminary clues as to the
`possible function of such genes in human disease.
`
`THE FUTURE IS HERE
`
`The near completion of the Human Genome Project
`has ensured an explosive start to the 21st century in
`the area of molecular medicine. The last decade has
`seen major advances in our understanding of the
`primary basis of many disorders across all subspecial-
`ties of medicine, based on fundamental, basic science
`
`Figure 1 From mutation to disease in hypertrophic
`cardiomyopathy. Gene mutations cause clinical disease.
`However, at least two important questions remain the
`focus of research now and in the future: what is the
`signalling pathway leading from a gene defect to the
`clinical phenotype (Q1) and how is this process modified
`by either genetic and/or environmental factors, such as
`exercise, gender, pharmaceutical agents etc. (Q2)?
`
`In terms of modifying the expression of the mutant
`gene, it has been widely reported that within a family
`with the same mutation there is marked variation in
`the severity of left ventricular hypertrophy and in the
`clinical manifestations in affected individuals.24–26,34,35
`Why is it that affected siblings can have such diverse
`phenotypes (i.e. asymptomatic versus sudden death)
`if they carry the same gene mutation? This
`phenomenon of clinical diversity, or ‘phenotypic
`heterogeneity’,
`is a hallmark of hypertrophic
`cardiomyopathy as well as other medical genetic
`conditions spanning numerous subspecialties (e.g.
`muscular dystrophies, Huntington’s disease, familial
`haemochromatosis and familial myeloproliferative
`diseases).36–39
`
`Such an observation implies that factors other than
`the underlying gene defect modify the expression of
`the mutant gene. These modifying factors may be
`genetic, for example a second gene that regulates the
`expression of the primary defect, or environmental
`factors, for example age, diet, exercise, gender and
`pharmaceutical agents. Clearly, the identification of
`such modifying factors has major implications in
`being able to alter the natural history of diseases such
`as hypertrophic cardiomyopathy. One potential
`genetic modifying factor that has been studied in
`human hypertrophic
`cardiomyopathy
`is
`the
`angiotensin-converting enzyme (ACE) gene. Some
`studies have indicated that the D allele of the ACE
`gene is associated with increased left ventricular
`hypertrophy and sudden death, implying that this
`potentially may be a modifying factor in the pheno-
`typic expression of the mutant gene.40,41 However, to
`define accurately such modifying factors, rodent
`models, whereby by genetic and environmental back-
`grounds can be controlled, will probably play a key
`role.
`
`00005
`
`

`

`58
`
`Semsarian & Seidman
`
`research. New genes are being discovered each week
`and the challenge ahead lies in determining what
`these genes do, how they function, how they interact
`with other genes as well as environmental influences
`and how they cause disease.
`
`However, to harness fully the potential of molecular
`genetics data for improving clinical medicine requires
`considerably more investigation and education.
`Analyses of the influence of genotype on disease
`expression and assessment of the effect of genotype on
`therapeutic response are likely to be early and impor-
`tant goals. Answering such questions requires
`collaborative efforts between clinicians and basic
`scientists. In this respect, the role of the ‘physician
`scientist’, or academic physician, which has received
`much attention
`in this Journal over the
`last
`12 months,45,46 will be of paramount importance. Such
`a person, for example a molecular cardiologist, would
`not only be in a prime position to identify appropriate
`areas for further research that have direct medical rele-
`vance, but would be the ideal ‘bridge’ between the
`basic scientists, full-time clinicians and patients.
`
`The advances made in our understanding of hyper-
`trophic cardiomyopathy illustrate the importance of
`molecular studies in human disease. Many disorders,
`previously thought of as environmental, are now being
`identified as having a genetic basis. The list grows
`each year. The thought of being able to modify such
`genes, and in some cases potentially correct the
`genetic defect, is an exciting prospect and is a glimpse
`of what lies ahead. The future, in terms of molecular
`medicine, has arrived.
`
`REFERENCES
`
`1 Macilwain C. World leaders heap praise on human genome
`landmark. Nature 2000; 405: 983–4.
`2 Seidman CE, Seidman JG. Gene mutations that cause familial
`hypertrophic cardiomyopathy. In: Haber E (ed.). Molecular
`Cardiovascular Medicine. New York: Scientific American,
`1995; 193–209.
`3 Seidman CE, Seidman JG. Molecular genetic studies of
`familial hypertrophic cardiomyopathy. Basic Res Cardiol
`1998; 93: 13–16.
`4 Schott JJ, Benson DW, Basson CT et al. Congenital heart
`disease caused by mutations in the transcription factor
`Nkx-2.5. Science 1998; 281: 108–11.
`5 Keating MT. Genetic approaches to cardiovascular disease:
`supravalvular aortic stenosis, Williams syndrome, and long
`QT syndrome. Circulation 1995; 92: 142–7.
`6 Dietz HC, Pyeritz RE. Mutations in the human gene for
`fibrillin-1 in the Marfan syndrome and related disorders.
`Hum Mol Genet 1995; 4: 1799–809.
`7 Turunen MP, Hiltunen MO,Yla-Herttuala S. Gene therapy
`for angiogenesis, restenosis and related diseases. Exp Gerontol
`1999; 34: 567–74.
`
`8 Stephan D, Weltin D, Zaric V. Gene therapy for coronary
`disease. Ann Endocrinol 2000; 61: 85–90.
`9 Isner JM. Angiogenesis: a breakthrough technology in
`cardiovascular medicine. J Invasive Cardiol 2000; 12: 7–14.
`10 Kibbe MR, Billiar TR, Tzeng E. Gene therapy for restenosis.
`Circ Res 2000; 86: 829–33.
`11 Teare D. Asymmetrical hypertrophy of the heart in young
`adults. Br Heart J 1958; 20: 1–8.
`12 Towbin JA, Roberts R. Cardiovascular diseases due to genetic
`abnormalities. In: Schlant RC, Alexander RW (eds). Hurst’s
`The Heart: Arteries and Veins. New York: Scientific American,
`1994; 1725–59.
`13 Spirito P, Seidman CE, McKenna WJ, Maron BJ. The
`management of hypertrophic cardiomyopathy. N Engl J Med
`1997; 336: 775–85.
`14 Maron BJ, Epstein SE, Roberts WC. Hypertrophic
`cardiomyopathy: a common cause of sudden death in the
`young competitive athlete. Eur Heart J 1983; 4: 135–42.
`15 Maron BJ, Epstein SE, Roberts WC. Causes of sudden
`death in competitive athletes. J Am Coll Cardiol 1986; 7:
`204–14.
`16 Maron BJ, Shirani J, Poliac LC, Mathenge R, Roberts WC,
`Mueller FO. Sudden death in young competitive athletes –
`clinical, demographic and pathological profiles. JAMA 1996;
`276: 199–204.
`17 Semsarian C, Richmond DR. Sudden cardiac death in
`familial hypertrophic cardiomyopathy. Aust NZ J Med 1999;
`29: 368–70.
`18 Fatkin D, Seidman JG, Seidman CE. Hypertrophic
`cardiomyopathy. In: Willerson JT, Cohn JN (eds).
`Cardiovascular Medicine. Philadelphia: Saunders (in press).
`19 Maron BJ, Gardin JM, Flack JM, Gidding SS, Bild D.
`Prevalence of hypertrophic cardiomyopathy in a general
`population of young adults: echocardiographic analysis of
`4111 subjects in the CARDIA Study. Circulation 1995; 92:
`785–9.
`20 MacRae CA, Ghaisas N, Kass S et al. Familial hypertrophic
`cardiomyopathy with Wolff-Parkinson-White syndrome maps
`to a locus on chromosome 7q3. J Clin Invest 1995; 96:
`1216–20.
`21 Maron BJ, Bonow RO, Cannon RO, Leon MB, Epstein SE.
`Hypertrophic cardiomyopathy: interrelations of clinical
`manifestations, pathophysiology and therapy. N Engl J Med
`1987; 316: 780–9 and 844–52.
`22 Watkins H, Seidman CE, Seidman JG, Feng HS, Sweeney
`HL. Expression and functional assessment of a truncated
`cardiac troponin T that causes hypertrophic cardiomyopathy:
`evidence for a dominant negative action. J Clin Invest 1996;
`98: 2456–61.
`23 Ryan MP, Cleland JG, French JA et al. The standard
`electrocardiogram as a screening test for hypertrophic
`cardiomyopathy. Am J Cardiol 1995; 76: 689–94.
`24 Watkins H, Rosenzweig A, Hwang D et al. Characteristics and
`prognostic implications of myosin missense mutations in
`familial hypertrophic cardiomyopathy. N Engl J Med 1992;
`326: 1108–14.
`25 Anan R, Greve G, Thierfelder L et al. Prognostic implications
`of novel β-cardiac myosin heavy chain gene mutations that
`cause familial hypertrophic cardiomyopathy. J Clin Invest
`1994; 93: 280–5.
`26 Nimura H, Bachinski LL, Sangwatanaroj S et al. Mutations in
`the gene for cardiac myosin-binding protein C and late-onset
`familial hypertrophic cardiomyopathy. N Engl J Med 1998;
`338: 1248–57.
`
`00006
`
`

`

`27 Semsarian C, Richmond DR. Difficulties in the diagnosis of
`apical hypertrophic cardiomyopathy. Aust NZ J Med 1998;
`28: 204–6.
`28 Maron BJ. Role of alcohol septal ablation in treatment of
`obstructive hypertrophic cardiomyopathy. Lancet 2000; 355:
`425–6.
`29 Maron BJ, Shen WK, Link MS et al. Efficacy of implantable
`cardioverter-defibrillators for the prevention of sudden death
`in patients with hypertrophic cardiomyopathy. N Engl J Med
`2000; 342: 365–73.
`30 Molkentin JD, Lu JR, Antos CL et al. A calcineurin-
`dependent transcriptional pathway for cardiac hypertrophy.
`Cell 1998; 93: 215–28.
`31 Sussman MA, Lim HW, Gude N et al. Prevention of cardiac
`hypertrophy in mice by calcineurin inhibition. Science 1998;
`281: 1690–3.
`32 Semsarian C, Wu MJ, Ju YK et al. Skeletal muscle
`hypertrophy is mediated by a Ca2+ dependent calcineurin
`signalling pathway. Nature 1999; 400: 576–81.
`33 Semsarian C, McConnell BM, Fatkin D et al. Cyclosporin A
`and minoxidil exacerbate cardiac hypertrophy in hypertrophic
`cardiomyopathy via a calcium-mediated pathway. Circulation
`2000; 102: 98.
`34 Solomon SD, Wolff S, Watkins H et al. Left ventricular
`hypertrophy and morphology in familial hypertrophic
`cardiomyopathy associated with mutations of the
`beta-myosin heavy chain gene. J Am Coll Cardiol 1993; 22:
`498–505.
`35 Semsarian C,Yu B, Ryce C et al. Sudden cardiac death in
`familial hypertrophic cardiomyopathy: are benign mutations
`really benign? Pathology 1997; 29: 305–8.
`
`Molecular medicine: gene therapy
`
`59
`
`36 Bonne G, Di Barletta MR, Varnous S et al. Mutations in the
`gene encoding lamin A/C cause autosomal dominant Emery-
`Dreifuss muscular dystrophy. Nat Genet 1999; 21: 285–8.
`37 Leavitt BR, Wellington CL, Hayden MR. Recent insights into
`the molecular pathogenesis of Huntington disease. Semin
`Neurol 1999; 19: 385–95.
`38 Sheth S, Brittenham GM. Genetic disorders affecting proteins
`of iron metabolism: clinical implications. Annu Rev Med
`2000; 51: 443–64.
`39 Gilbert HS. Familial myeloproliferative disease. Baillieres Clin
`Haematol 1998; 11: 849–58.
`40 Marian AJ,Yu QT, Workman R, Greve G, Roberts R.
`Angiotensin-converting enzyme polymorphism in
`hypertrophic cardiomyopathy and sudden death. Lancet 1993;
`342: 1085–6.
`41 Lechin M, Quinones MA, Omran A et al. Angiotensin-I
`converting enzyme genotypes and left ventricular hypertrophy
`in patients with hypertrophic cardiomyopathy. Circulation
`1995; 92: 1808–12.
`42 Watson JD, Crick FH. Molecular structure of nucleic acids: a
`structure for deoxyribose nucleic acid. Nature 1953; 171:
`737–8.
`43 Pennisi E. Finally, the Book of Life and instructions for
`navigating it. Science 2000; 288: 2304–7.
`44 Pennisi E. And the gene number is …? Science 2000; 288:
`1146–7.
`45 Larkins RG. The clinician-scientist in the 21st century. Aust
`NZ J Med 2000; 30: 68–70.
`46 Burke D. Economic rationalism in health and education;
`impact of the academic physician. Aust NZ J Med 2000; 30:
`71–4.
`
`00007
`
`