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A family study and the natural history of prenatally detected unilateral multicystic dysplastic kidney.

PURPOSE: We document the inheritance pattern of multicystic dysplastic kidney in 3 affected families and screen first-degree relatives of a cohort of children with prenatally detected multicystic dysplastic kidney for renal anomalies. The study also afforded an opportunity to document the natural history of prenatally detected multicystic dysplastic kidney. MATERIALS AND METHODS: We identified 3 families during clinical treatment of children with prenatally detected multicystic dysplastic kidneys. Other members of these families were evaluated with renal ultrasonography. For the family screening study index cases were identified from a fetal uropathy database. A total of 94 first-degree relatives (52 parents, 35 full siblings and 7 half siblings) of 29 children with prenatally detected multicystic dysplastic kidneys were studied with urinary tract ultrasonography, blood pressure measurement, urinalysis and plasma biochemistry. RESULTS: Two families had affected sibling pairs, 1 of which also had a half sibling with vesicoureteral reflux. The third family included 3 individuals with multicystic dysplastic kidney and 1 with renal agenesis thought to have resulted from involution of multicystic dysplastic kidney. This family is consistent with autosomal dominant inheritance with variable expressivity and reduced penetrance. In the screening study ultrasonography did not demonstrate significant renal anomalies in any of the 94 first-degree relatives of the multicystic dysplastic kidney index cases. Followup assessment of prenatally detected multicystic dysplastic kidneys in index cases demonstrated total involution in 52% at a median age of 6.5 years with no multicystic dysplastic kidney related morbidity. CONCLUSIONS: Multicystic dysplastic kidney can be familial but is most commonly a sporadic anomaly. Formal screening of relatives is not recommended. Followup data on a cohort of children with prenatally detected multicystic dysplastic kidney add further support to conservative management.

Female↗

Dominant negative mechanism underlies autosomal dominant Stargardt-like macular dystrophy linked to mutations in ELOVL4.

ELOVL4 (elongation of very long chain fatty acids 4) is a member of the ELO family of proteins involved in the biosynthesis of very long chain fatty acids. Protein truncation mutations in ELOVL4 have been identified in patients with autosomal dominant Stargardt-like macular degeneration. To determine whether a dominant negative mechanism is responsible for the autosomal dominant inheritance pattern of this disease, we studied the subcellular localization and interaction of wild type and mutant ELOVL4 in COS-7 and HEK 293T cultured cells by immunofluorescence and co-immunoprecipitation. Wild type ELOVL4 containing an endoplasmic reticulum retention sequence was localized to the endoplasmic reticulum as expected. In contrast, disease-associated C-terminal truncation ELOVL4 mutants accumulated as large inclusions exhibiting aggresome-like characteristics in a juxtanuclear position within COS-7 cells. When the wild type and mutant proteins were co-expressed incultured cells, wild type ELOVL4 co-purified with mutant ELOVL4 on an immunoaffinity column and co-localized with the mutant protein in aggresome-like inclusions adjacent to the nucleus. These results indicate that wild type and mutant ELOVL4 form a complex that exhibits an abnormal subcellular localization found for individually expressed mutant ELOVL4. From these studies, we conclude that disease-linked C-terminal truncation mutants of ELOVL4 exert a dominant negative effect on wild type ELOVL4, altering its subcellular localization. This dominant negative mechanism contributes to the autosomal dominant inheritance of Stargardt-like macular dystrophy.

Amino Acid Motifs↗

Factor VNew Brunswick: Ala221-to-Val substitution results in reduced cofactor activity.

We have characterized the factor V protein and cDNA of a patient displaying factor V deficiency (parahemophilia) and correlated the reduced activity with a missense mutation of Ala221-to-Val. Plasma from the subject individual (C1) presented reduced factor V antigen (39% of normal) that displayed reduced activity (approximately 26% of normal). Factor V purified from this individual by standard techniques shows normal migration on sodium dodecyl sulfate gels and a normal pattern of activation by thrombin. Purified antigen from sibling C2 gives a much reduced specific activity of 263 U/mg (17% of normal). Sibling C3, the mother, and the father have antigen within the normal range (57% to 200%) that has approximately normal specific activity. The cDNA encoding the factor Va heavy and light chains of the subject individual was polymerase chain reaction-amplified and sequenced and revealed an A-to-G substitution at position 3 of codon 51 (silent mutation), a C-to-T substitution in position 2 of codon 221 (Ala221-Val), a T-to-C substitution at position 3 of codon 708 (silent mutation), and a G-to-A substitution at position 1 of codon 2185 (Thr2185-Ala). The latter mutation was also observed in control individuals and is proposed to be a possible polymorphism. Restriction analyses demonstrated the presence of one mutant and one normal allele in the father. The subject individual (C1) and sibling C2 carry only the mutant allele. The mother and sibling C3 carry only the normal allele. The inheritance pattern suggests the presence of a missing or nonexpressed allele in the mother that is passed on to all the siblings. Expression of only the mutant allele by the subject individual (C1) and sibling C2 is consistent with reduced factor V antigen and activity in these patients. We have designated this mutant as Factor VNew Brunswick.

Adolescent↗

Genetic analysis of Japanese pedigrees with Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is a maternally transmitted disease, characterized by bilateral optic atrophy mainly in young men. The strict maternal inheritance pattern of LHON can be explained by specific primary mitochondrial (mt) DNA mutations. However, intrafamilial phenotypic variation requires additional pathogenetic factors. Homo- or heteroplasmy of the primary mtDNA mutation, synergistic or antagonistic effects of secondary mtDNA mutations co-existing with the primary mutation, and involvement of an X-linked recessive gene have been postulated to be such factors. In an attempt to determine whether one of the three factors affects LHON expression in Japanese pedigrees, mtDNA analyses by means of RFLP and Southern blot hybridization of PCR products were performed for 22 members in 10 LHON pedigrees, and segregation analysis were conducted for 82 published LHON pedigrees. All of the LHON maternal relatives tested possessed only a homoplasmic mtDNA mutation at position 11778 with none of the secondary mtDNA mutations. Taking into account an extremely high prevalence of the 11778 mutation in Japanese LHON pedigrees (approximately 90%), the results indicated homogeneity of the mitochondrial mutation in Japanese LHON pedigrees. On the other hand, a goodness-of-fit test revealed that the two-locus mitochondrial and X-linked gene control theory accorded well with the characteristic inheritance trait of predominance in males and reduced penetrance with late onset in females. However, the penetrance in heterozygous LHON maternal line females of Japanese pedigrees was about twice as high as that in foreign pedigrees, indicating an ethnic difference in LHON genetics.

DNA, Mitochondrial↗

Molecular biology of hereditary enamel defects.

Amelogenesis imperfecta is a disfiguring inherited condition affecting tooth enamel. X-Linked and autosomal dominant and recessive inheritance patterns occur. X-Linked amelogenesis imperfecta has been studied extensively at the molecular level. Linkage analysis has shown that there is genetic hetetogeneity in X-linked amelogenesis imperfecta with two identified loci: AIH1 and AIH3. The AIH1 locus corresponds to the location of the amelogenin gene on the distal short arm of the X chromosome; various mutations in the amelogenin gene have been found in families with X-linked amelogenesis imperfecta. The AIH3 locus maps to the Xq24-q27.1 region on the long arm of the X chromosome. Linkage to the long arm of chromosome 4 has been established in three families with autosomal dominant amelogenesis imperfecta. There is as yet no published evidence for genetic heterogeneity in autosomal dominant amelogenesis imperfecta as in X-linked amelogenesis imperfecta. Candidate genes for autosomal dominant amelogenesis imperfecta include tuftelin (1q), albumin (4q) and ameloblastin (4q) but the involvement of these genes in the disease has yet to be demonstrated. In view of the variable clinical appearances within families with autosomal dominant amelogenesis imperfecta and X-linked amelogenesis imperfecta, together with the finding that different X-linked amelogenesis imperfecta phenotypes result from mutations within the same gene, an alternative classification based on the molecular defect and mode of inheritance rather than phenotype has been proposed.

Amelogenesis Imperfecta↗

Pedigree models for complex human traits involving the mitochondrial genome.

Recent biochemical and molecular-genetic discoveries concerning variations in human mtDNA have suggested a role for mtDNA mutations in a number of human traits and disorders. Although the importance of these discoveries cannot be emphasized enough, the complex natures of mitochondrial biogenesis, mutant mtDNA phenotype expression, and the maternal inheritance pattern exhibited by mtDNA transmission make it difficult to develop models that can be used routinely in pedigree analyses to quantify and test hypotheses about the role of mtDNA in the expression of a trait. In the present paper, we describe complexities inherent in mitochondrial biogenesis and genetic transmission and show how these complexities can be incorporated into appropriate mathematical models. We offer a variety of likelihood-based models which account for the complexities discussed. The derivation of our models is meant to stimulate the construction of statistical tests for putative mtDNA contribution to a trait. Results of simulation studies which make use of the proposed models are described. The results of the simulation studies suggest that, although pedigree models of mtDNA effects can be reliable, success in mapping chromosomal determinants of a trait does not preclude the possibility that mtDNA determinants exists for the trait as well. Shortcomings inherent in the proposed models are described in an effort to expose areas in need of additional research.

Computer Simulation↗

Candidate gene case-control association studies: advantages and potential pitfalls.

There is increasing information on the importance of genetic polymorphisms in human genes. Polymorphisms occur on average once every 500-1000 base pairs in the human genome and are useful in the identification of genes involved in human disease. Some genetic polymorphisms have functionally significant effects on the gene product and are the most useful type of polymorphism in disease association studies while others are simply useful markers. There are two main approaches using polymorphisms in the identification of genes involved in polygenic diseases. The first involves examining inheritance patterns for genetic polymorphisms in family studies and the second case-control studies which compare genotype frequencies for candidate disease genes in unrelated individuals with the disease and healthy controls. Use of family studies is generally the preferred approach but this is only feasible if the genetic component of the disease is relatively strong, DNA samples are available from other family members and the disease is relatively easy to diagnose and is not stigmatized. Population case-control studies are useful both as an alternative and an adjunct to family studies. When performing case-control studies factors such as study design, methods for recruitment of cases and controls, functional significance of polymorphisms chosen for study and statistical analysis of data require close attention to ensure that only genuine associations are detected. To illustrate some potential problems in the design and interpretation of association studies, some specific examples of association studies on drug response and on disease susceptibility involving receptor genes, cytochrome P450 and other xenobiotic metabolizing enzyme genes and immune system genes including TNF-alpha, IL-10 and the IL-4 receptor are discussed.

Case-Control Studies↗

Familial neurological disease associated with spongiform encephalopathy.

In a family in whom susceptibility to neurological diseases was transmitted in autosomal dominant fashion, the diseases affecting different family members ranged from subacute and chronic dementias to various motor system abnormalities without dementia. The propositus suffered a typical clinical course of Creutzfeldt-Jakob disease. Neuropathological observations revealed spongiform encephalopathy. A first cousin had a chronic dementia; no spongiform changes were present at autopsy. Both patients had PAS-positive, eosinophilic plaques throughout the brain. Muscle biopsy of the propositus revealed some changes suggestive of "ragged-red" myopathy. The heterogeneity of disease and the inheritance pattern in this family suggests that general susceptibility to neurological disease is a genetic trait.

Adult↗

Severe neonatal centronuclear myopathy with autosomal dominant inheritance.

We studied a boy with severe infantile centronuclear myopathy (CNM) and his mother with clinical, electrophysiological, and pathological signs of skeletal muscle, peripheral nerve, and brain-stem disorder, and we believe that her condition represents a variation of her son's disease. His brother had similar symptoms and died at 4 days of age. The occurrence of this syndrome in a symptomatic mother and two severely affected sons suggests an autosomal dominant inheritance with variable expressivity. To our knowledge, this inheritance pattern has not been previously reported in severe (fatal) infantile CNM. The different courses in the mother and her offspring may be manifestations of a single or separate abnormal gene causing alteration of muscle and nerve maturation.

Child↗

Familial essential tremor in 4 kindreds. Prospects for genetic mapping.

OBJECTIVES: To describe 4 large families with essential tremor (ET) to draw attention to the marked clinical heterogeneity of ET. To use computer simulation analysis to provide information about the power of the family material for future linkage studies. SUBJECTS: We examined a total of 251 members from 4 kindreds with ET. The mean (+/-SD) age at onset of ET varied among the 4 kindreds between 19.0 +/- 11.4 years and 45.6 +/- 7.4 years. Three of the kindreds had a total of 41 members with the combination of ET and dystonia, typically manifested as torticollis or dystonic writers' cramp. In 1 of the kindreds, ET seemed to be associated with malignant hyperthermia. One kindred represented "pure" ET without any associated disorders. METHODS: In addition to detailed clinical assessments, we conducted computer simulations on the families' pedigrees using a model that presumed an autosomal dominant inheritance pattern with high penetrance. RESULTS: Although there was evidence of clinical heterogeneity between the families, the duration of symptoms directly correlated with the severity of disease. The computer simulations indicated that 3 of the 4 pedigrees had enough power to generate a significant linkage result in a total genome search with highly polymorphic markers. CONCLUSIONS: This study confirms the frequent coexistence of ET and dystonia in individual families. Computer simulations can be used to determine the power of the family to detect a linked marker. Identification of the defective gene(s) will enable a better understanding and classification of these common movement disorders.

Aged↗

A gene for Parkinson disease.

Until recently, the possibility that genetic factors contributed significantly to the pathogenesis of Parkinson disease (PD) was accorded relatively short shift. Few patients with obviously familial PD are seen in common practice, and families with parkinsonism often present with rather atypical features. The discovery that the neurotoxin N-methyltetrahydropyridine (MPTP) rapidly induces an illness similar to sporadic PD added fuel to those arguing that environmental factors must be largely responsible. But more recently, this view has begun to shift because no generally plausible environmental factors emerged and data favoring a genetic component began to mount. Now it is clear that the cause of PD may on occasion be purely genetic and involve autosomal dominant as well as various other inheritance patterns. Moreover, it has become increasingly apparent that even in sporadic cases, the disease most likely reflects some combination of genetic susceptibility and environmental insult. In such instances, the genetic component presumably acts by increasing the vulnerability of dopamine-containing neurons in the nigrostriatal system to injury by 1 or more common, possibly by themselves relatively innocuous, environmental factors. This view has now been substantially reinforced and our ability to understand the pathogenesis of PD dramatically advanced by the recent identification of a gene responsible for PD in 4 unrelated families.

Environment↗

Clinical features and disease haplotypes of individuals with the N279K tau gene mutation: a comparison of the pallidopontonigral degeneration kindred and a French family.

BACKGROUND: An N279K missense mutation in exon 10 of the tau gene reported in an American family with pallidopontonigral degeneration (PPND family) was recently found in members of a French kindred with dementia and supranuclear palsy. OBJECTIVES: To compare clinical phenotypes of both families and to perform genealogical and molecular genetic studies to determine whether they are derived from a common founder. DESIGN AND METHODS: We performed clinical examinations of affected members of both families and compared clinical phenotypes, existing genealogical family records, and chromosome 17 microsatellite repeat markers in the vicinity of the tau gene. RESULTS: The inheritance pattern is autosomal dominant in the PPND family and appears so in the French family. Average age at onset of clinical symptoms was 43 years in the PPND family and 41 years in the French family. Mean disease duration was 8 years in the PPND family and 6 years in the French family. Parkinsonism, personality changes, and dementia of the frontotemporal type were seen in both kindreds. All affected patients exhibited rapidly progressive parkinsonism characterized by bradykinesia, tremor, postural instability, and rigidity. Some had a transient response to levodopa therapy during the initial stages. Pyramidal signs and eye movement abnormalities, including supranuclear gaze palsy, were common. Results of linkage studies of the tau region in chromosome 17 did not reveal a haplotype common to both kindreds. CONCLUSIONS: Affected members from both families had more clinical similarities than differences. Results of genealogical and molecular genetic studies determined that the families were not related. The N279K mutations found in both families have independent origins.

Adult↗

Frequency analysis and clinical characterization of spinocerebellar ataxia types 1, 2, 3, 6, and 7 in Korean patients.

BACKGROUND: By genetic analysis, the CAG repeat expansion has been established in spinocerebellar ataxia (SCA) types 1, 2, 3, 6, and 7. Despite the genetic differentiation of SCA, the characterization of the phenotypes of various SCAs has been challenging for better clinical diagnosis. OBJECTIVE: To analyze the frequencies and the clinical manifestations of SCA1, SCA2, SCA3, SCA6, and SCA7 in Korean patients. PATIENTS AND METHODS: We performed genetic analysis in 253 unrelated Korean patients with progressive cerebellar ataxia. We compared the frequencies, inheritance patterns, and various clinical manifestations of patients with genetically confirmed SCA. RESULTS: Among the 52 patients with expanded CAG repeat, the most frequent SCA type was SCA2, followed by SCA3, SCA6, SCA1, and SCA7. Nine patients (17%) had a negative family history of ataxia, mostly in SCA6. There were characteristic clinical features such as hypotonia and optic atrophy for SCA1; hyporeflexia for SCA2; nystagmus, bulging eye, and dystonia for SCA3; and macular degeneration for SCA7. Interestingly, 4 patients (1 with SCA2, 1 with SCA3, and 2 with SCA6) were misdiagnosed as having multiple-system atrophy because of the absence of family history and the presence of parkinsonism and urinary incontinence. CONCLUSIONS: This study provides a detailed analysis of the clinical characteristics of the genetically defined CAG-repeat SCAs in Korean patients. Although phenotypes were heterogeneous, some clinical features may be helpful for clinical diagnosis. However, genetic studies for SCA are needed despite uncertain family history or the presence of atypical clinical features causing misdiagnosis as atypical parkinsonism.

Adult↗

Novel presenilin 1 mutation (S170F) causing Alzheimer disease with Lewy bodies in the third decade of life.

BACKGROUND: Cases of early-onset Alzheimer disease (AD) with an autosomal dominant inheritance pattern (familial AD [FAD]) are rare but have greatly advanced our understanding of the molecular pathogenesis of AD. We describe herein a kindred with very early-onset FAD (age, <40 years) with unusual pathological features and a novel mutation in the presenilin 1 (PSEN1) gene (S170F) and review the existing literature on very early-onset FAD. OBJECTIVE: To analyze the neuropathological and genetic features of a family with onset of AD in the third decade of life. DESIGN, SETTING, AND PARTICIPANTS: The proband underwent full clinical assessment and postmortem examination at the Washington University Alzheimer's Disease Research Center, St Louis, Mo. Limited pathological samples and autopsy records of 2 affected family members were available. The proband underwent screening for mutations in genes linked with FAD. RESULTS: Dementia developed in 3 family members in this kindred at a mean age of 27 years; the proband had myoclonus, seizures, and rigidity, similar to findings in previously described kindreds with PSEN1 mutations. All 3 family members were confirmed to have AD by neuropathological examination. The proband also had widespread Lewy body pathology in the brainstem, limbic areas, and neocortex; specific staining for Lewy bodies was not performed in the other 2 family members. The proband had a single mutation (S170F) in exon 6 of the PSEN1 gene, which segregates with disease. CONCLUSIONS: A novel PSEN1 mutation causes very-early-onset FAD with associated Lewy bodies. To our knowledge, this kindred has the earliest reported onset of pathologically confirmed FAD and dementia with Lewy bodies.

Adult↗

Value of gradient-echo magnetic resonance imaging in the diagnosis of familial cerebral cavernous malformation.

BACKGROUND: Cerebral cavernous malformations (CCMs) are congenital vascular anomalies that can cause seizures, intracranial hemorrhages, focal neurological deficits, and migrainelike headaches. Magnetic resonance (MR) imaging has substantially facilitated diagnosis of CCM. It is now widely accepted that familial clustering with an autosomal dominant inheritance pattern should be suspected in cases of multiple lesions. OBJECTIVE: To determine by MR imaging the penetrance of cavernous malformations in a 3-generation family that included 5 members with typical clinical signs and diagnostic findings. METHODS: All family members underwent routine MR T1-weighted and T2-weighted spin-echo sequences in addition to MR T2-weighted gradient-echo sequences. RESULTS: Four family members had been symptomatic with either brainstem bleeding, headaches, or focal neurological signs. The gradient-echo sequences yielded a dramatically higher sensitivity with regard to lesion number and distribution. As in previous reports of familial CCM, an increase in lesion number with increasing age, changes in lesion characteristics, de novo occurrence in serial MR imaging over time, and the phenomenon of anticipation could be confirmed in this family. CONCLUSION: Magnetic resonance gradient-echo sequences should be considered the method of choice for diagnosis of familial CCM.

Adult↗

Molecular basis of low-penetrance retinoblastoma.

Retinoblastoma is a malignant tumor of the retina that occurs primarily in young children as a result of mutations in the retinoblastoma gene (RB), the first tumor suppressor gene to be identified. In about 35% to 40% of patients with retinoblastoma, an RB gene mutation is present in the germline, resulting in hereditary transmission of the disease. Most families with hereditary retinoblastoma demonstrate autosomal dominant inheritance with almost complete penetrance and high expressivity. However, some families display an inheritance pattern characterized by reduced penetrance and expressivity. Recent advances in our understanding of the structure and function of the retinoblastoma protein (pRB) now provide new insights into the molecular basis of this low-penetrance form of retinoblastoma. Low-penetrance retinoblastoma mutations either cause a reduction in the amount of normal pRB that is produced (class 1 mutations) or result in a partially functional mutant pRB (class 2 mutations).

Genes, Retinoblastoma↗

Hereditary congenital alacrima.

We describe a family with markedly deficient lacrimation from infancy and punctate corneal epithelial erosions. An autosomal dominant inheritance pattern is suggested. A hypoplasia of the lacrimal gland in this family was suggested by pharmacologic testing and by histopathologic examination of the lacrimal gland of the proposita. The family investigated in this report represents the first instance of hereditary congenital alacrima without associated ocular or adnexal abnormalities and apart from systemic disorders such as the Riley-Day syndrome and anhidrotic ectodermal dysplasia.

Adolescent↗

Visual field changes in cone-rod degenerations.

The visual field test results from 20 patients with con-rod degeneration (CRD) from all inheritance patterns were reviewed. Typical fundus findings of CRD included optic disc pseudoedema, temporal disc atrophy, parapapillary and disc telangiectasis, and few to no retinal pigmentary deposits. Visual field changes were seen to be distinctive and, like electrophysiologic tests, were helpful in pointing to a retinal degenerative process rather than an optic neuropathy.

Adolescent↗