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PubMed1989

Definition and properties of disequilibria within nuclear-mitochondrial-chloroplast and other nuclear-dicytoplasmic systems.

We define and determine the interrelationships among five sets of disequilibrium parameters that measure two- and three-locus nonrandom associations in nuclear-dicytoplasmic systems. These assume a diploid nuclear locus and two haploid cytoplasmic loci, with special reference to nuclear-mitochondrial-chloroplast systems. Three sets of two-locus disequilibria measure the association between haplotypes at the two cytoplasmic loci (DMC) and associations between each cytoplasmic locus and nuclear alleles or genotypes (DM, D1M, D2M, D3M; DC, D1C, D2C, D3C). In addition, we present two classes of higher-order disequilibria that measure nonrandom allelic or genotypic associations involving all three loci. The first class quantifies associations between the nuclear locus and the two cytoplasmic loci taken jointly (DA/MC, DAA/MC, DAa/MC, Daa/MC, etc.), whereas the second measures only those associations remaining after all two-locus associations have been taken into account (DA/M/C, DAA/M/C, DAa/M/C, Daa/M/C). Based on combinations of these five sets of measures, we suggest a variety of parameterizations of three-locus, nuclear-dicytoplasmic systems. The dynamics of these disequilibria are then investigated under models of random and mixed mating, either with both cytoplasmic genomes inherited through the same parent or through opposite parents. Except for associations between the cytoplasmic haplotypes, which are constant when the two cytoplasmic genomes are inherited through the same parent, all disequilibria ultimately decay to zero. These randomizations do not necessarily occur monotonically, however, and in some cases are preceded by an initial increase in magnitude or sign change. For both inheritance patterns, the asymptotic decay rates are steadily retarded by increasing levels of self-fertilization. This behavior contrasts with that in the extreme case of complete selfing, for which only the heterozygote disequilibria always decay to zero. For all models considered, the dynamics of the two-locus cytonuclear subsystems are solely a function of the mating system, whereas the dynamical behavior and sign patterns of the cytoplasmic and three-locus disequilibria also depend strongly on the mode of cytoplasmic inheritance.

Cell Nucleus↗
PubMed1997

Diaphragmatic hernia-exomphalos-hypertelorism syndrome: a new case and further evidence of autosomal recessive inheritance.

We describe a male patient with wide anterior fontanel and metopic suture, hypertelorism, down slanting palpebral fissures, bilateral iris coloboma, omphalocele, and bilateral absence of the diaphragm with herniation of abdominal organs causing pulmonary hypoplasia and death. Autopsy also showed intestinal malrotation. All findings in this case are consistent with those described as a newly recognized syndrome by Donnai and Barrow [1993]. Since the parents are first cousins, this case provides further evidence for the previously postulated autosomal recessive inheritance pattern. Follow-up on the patients and families reported by Donnai and Barrow [1993] also supports autosomal recessive inheritance.

Adult↗
PubMed1984

DNA methylation versus gene expression.

Vertebrate DNA is methylated at a high proportion of cytosine residues in the sequence CpG, and it has been suggested that the distribution of methylated and non-methylated CpGs in a given cell type influences the pattern of gene expression in those cells. Since a DNA methylation pattern is normally transmitted faithfully to daughter cells via cell division, this idea suggests an origin for stable, clonally inherited patterns of gene expression. This article discusses some of the current evidence for a relationship between DNA methylation and gene expression. Although the evidence is incomplete, it appears already that the relationship is variable: transcription of some genes is repressed by the presence of 5-methylcytosine at certain CpGs, and may be controlled by methylation, while transcription of other genes is indifferent to methylation. In attempting to explain this variability it is helpful to adopt an evolutionary perspective.

5-Methylcytosine↗
PubMed1997

Scoliosis in twins. A meta-analysis of the literature and report of six cases.

STUDY DESIGN: This study is a meta-analysis of the world's literature on adolescent idiopathic scoliosis in monozygotic and dizygotic twins. Additionally, six previously unreported cases of scoliosis in twins are presented. OBJECTIVES: To compare and contrast the concordance, severity, and curve patterns in monozygotic and dizygotic twins with adolescent idiopathic scoliosis in an attempt to document a genetic etiology and delineate inheritance patterns for adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: There are numerous case reports of twins sets with adolescent idiopathic scoliosis. However, this data has not been previously analyzed as a single data base. METHODS: The literature was searched for cases of twins with adolescent idiopathic scoliosis, and six cases of patients treated by authors were added. One hundred cases of sets of twins were discovered, 68 of which had sufficient data for comparative analysis. Each set was evaluated for monozygosity, concordance of scoliosis, curve pattern, and severity of curve. RESULTS: Thirty-seven sets of twins were monozygous, and 31 sets were dizygous. Concordance was 73% among monozygous twins and 36% among dizygous twins. The difference is statistically significant at P < 0.003. Curve severity could be compared in 20 sets of monozygous twins and 16 sets of dizygous twins. Among monozygous twins, there was a correlation coefficient of r = 0.399 (P < 0.126). Curve pattern comparison was not statistically significant. CONCLUSIONS: Monozygous twins have a significantly higher rate of concordance than dizygous twins, and the curves in monozygous twins develop and progress together. Based on these data, there is strong evidence for a genetic etiology for adolescent idiopathic scoliosis.

Adolescent↗
PubMed1993

Duchenne-Becker muscular dystrophy and the nondystrophic myotonias. Paradigms for loss of function and change of function of gene products.

Recessively inherited disorders can most often be considered loss of function: the patient has only defective copies of the defective gene (homozygous or hemizygous), with little or no functional protein products produced. Dominantly inherited disorders can most often be considered change of function: the patient has both mutant and normal copies of the gene (heterozygous); however, the mutant gene produces an abnormal protein product that causes dysfunction of the cell. Categorization of inherited disorders simply by their inheritance pattern thus affords some predictions concerning the underlying biochemical defect. To illustrate these generalizations, the molecular data on two important human inherited neurologic disorders will be described. X-linked recessive Duchenne/Becker muscular dystrophy has been shown to caused by loss of function of the dystrophin product. Dominantly inherited hyperkalemic periodic paralysis and paramyotonia congenita have been shown to be the result of single amino acid changes of the skeletal muscle voltage-sensitive sodium channel that alter the channel's function in response to environmental or physiologic stimuli (change of function).

Dystrophin↗
PubMed1984

The heterogeneity of distal arthrogryposis.

A study of distal arthrogryposis is described including neurology, electromyography, cerebral and muscular CT-scanning, and muscle and nerve biopsies. In four cases presenting with congenital distal contractures, various neuromuscular disorders were diagnosed. They were respectively, congenital myopathy with core-like structures, congenital hypertrophic neuropathy, axonal neuropathy and anterior horn cell disease. The role of cerebral disorders in the pathogenesis of distal contractures is also considered. The significance of abnormal dermatoglyphics in the determination of the prenatal time of onset of congenital myopathies and arthrogryposis is discussed. Our findings provide evidence for the hypothesis that distal arthrogryposis may not be a distinct clinical entity with an autosomal dominant inheritance pattern, but a symptom, indicating various cerebral, neuromuscular and connective tissue disorders, present in numerous congenital syndromes with different modes of inheritance. In addition the value of electromyography, nerve conduction velocity studies, muscle and cerebral CT-scanning, and histology of muscle and nerve biopsies in the differential diagnosis of (distal) arthrogryposis is stressed.

Adolescent↗
PubMed1998

Gene defect behind APECED: a new clue to autoimmunity.

The molecular background of human autoimmunity is poorly understood. Although many autoimmune diseases have a genetic basis, the actual disease appearance results from a complex interplay between genes and environment and thus these diseases represent typical multifactorial diseases. Even with molecular tools provided by the Human Genome Project, it still remains a challenge to identify the predisposing DNA variants behind such multifactorial traits. Two strategies have been suggested to provide short-cuts to the dissection of the genetic background of complex autoimmune diseases: (i) identification of genes in rare human diseases with a strong autoimmune component or (ii) unravelling loci causing phenotypes resembling autoimmune diseases in inbred mice strains. Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a monogenic autosomal disease with a recessive inheritance pattern, characterized by multiple autoimmune endocrinopathies, chronic mucocutaneous candidiasis and ectodermal dystrophies. Since it is the only known human autoimmune disease inherited in a Mendelian fashion, it provides an excellent model to analyse the genetic component of human autoimmunity. The causative gene for APECED was isolated recently by a traditional positional cloning strategy by two independent groups. The cDNA for the APECED gene proved to originate from a novel gene, AIRE , which is expressed prevalently in thymus, pancreas and adrenal cortex. Multiple mutations in AIRE have been identified in APECED patients. The predicted proline-rich AIRE polypeptide harbours two PHD-type zinc finger motifs and contains a putative nuclear targeting signal suggesting its involvement in the regulation of transcription. In the future, functional analysis of the AIRE protein both in vitro and in vivo will provide valuable insight not only into the molecular pathogenesis of APECED but also into the aetiology of autoimmunity in general.

Animals↗
PubMed1993

Variable phenotypic expression of genotypic abnormalities in the porphyrias.

The inherited porphyrias are the consequence of inherited deficiencies of enzymes in the heme synthesis pathway; they exhibit classical Mendelian inheritance patterns. The acute porphyrias (acute intermittent, porphyria variegata, hereditary coproporphyria) result from 50% (approx.) deficiencies of specific enzymes, which demonstrate autosomal dominant inheritance. However, only approx. 10% of subjects who inherit a porphyrin enzyme deficiency develop the corresponding acute porphyria and in most instances there is no obvious reason why one patient with an enzyme deficiency is symptomatic whereas another is not. Control of heme synthesis is achieved by the repressor effect of heme on the enzyme ALA synthase. Acute attacks of porphyria can be precipitated in susceptible persons by drugs, ethanol, starvation, hormones, stress and infection. The mechanism is usually by induction of ALA synthase activity. The molecular biology of porphyria variegata and hereditary coproporphyria is large unexplored. Acute intermittent porphyria is due to a partial deficiency of the enzyme porphobilinogen deaminase in the liver. The location of the gene for this enzyme has been identified on the long arm of chromosome 11. Acute intermittent porphyria is a genetically heterogenous disease with the abnormality frequently being a point mutation affecting synthesis of the enzyme.

Gene Expression↗
PubMed1994

Nucleolar size polymorphisms in commercial layer chickens; determination of incidence, inheritance, and nucleolar sizes.

In the chicken, one chromosome pair encodes the ribosomal (r)RNA genes and two nucleoli are formed in interphase cells. The nucleolus is the site of rRNA synthesis and ribosome biogenesis. Nucleolar size polymorphisms have been detected in research strains of chickens and found to represent heterozygosity for rRNA gene copy number. The objectives of the present study were to determine whether nucleolar size polymorphisms exist in commercial chicken flocks and whether such polymorphisms are under genetic control. The occurrence of nucleolar size polymorphisms was studied in three lines of commercial layer chickens (designated A, B, and C). Nucleolar size polymorphisms were found in all three lines. However, the lines differed in the proportion of individuals exhibiting the polymorphic phenotype of two unequal-sized nucleoli (2P). The 2P phenotype, determined in successive years, was found in 10 to 14% of Line A birds, 18 to 23% of Line B birds, and 41 to 63% of Line C birds. The inheritance pattern of the nucleolar size polymorphism and nucleoli sizes were studied in Line C birds. The 2P phenotype was found to be inherited in Mendelian fashion. The large nucleolus was 1.7x and 1.6x that of the smaller nucleolus in 2P males and females, respectively, and was larger than the nucleoli of 2E birds (2E = nonpolymorphic phenotype of two equal-sized nucleoli). Total nucleolar size was greater in cells of 2P birds than in cells of 2E birds. These data suggest that the genetic basis for the large nucleolus in Line C 2P cells is a "larger than normal" rDNA cluster.

Animals↗
PubMed1992

Prevalence of retinitis pigmentosa and allied disorders in Denmark. III. Hereditary pattern.

A national epidemiological study revealed 1301 prevalent cases of retinitis pigmentosa (RP) in the Danish population on January 1, 1988. The corresponding number of 974 families were analyzed with respect to Mendelian inheritance groups. Thirty families, comprising 6.9% of the prevalent RP-cases, were categorized with an autosomal dominant inheritance pattern. In 187 families, 22.6% of RP-cases, autosomal recessive heredity was encountered. X-linked heredity was found in 45 families, 10.8% of the RP-cases. Simplex RP-cases comprised 562 persons (43.2% of RP-cases). About a fourth of the non-systemic X-linked cases were females. Half of these had an age at onset after 30 years, but a third had their first RP-symptoms before age 18 years. A representative fraction of parents to non-systemic autosomal dominant, autosomal recessive, X-linked, and simplex cases were evaluated concerning their age at the time they had their first affected child. Mothers of the male simplex cases were of statistically significant higher age than mothers of the other inheritance groups. This may imply a high rate of new mutations among simplex cases, especially on the X-chromosome.

Adolescent↗
PubMed1978

Reticular dystrophy of the retinal pigment epithelium. A clinical and electrophysiologic study of three generations.

Reticular dystrophy of the retinal pigment epithelium is characterized by a posterior pattern of pigment clumping like a "fishnet with knots." Four patients in three successive generations were seen with typical reticular dystrophy. A fifth patient had abnormal dark adaptation. In this family reticular dystrophy was characterized by the typical reticular pigmentary pattern, good visual acuity, normal electroretinographic findings, abnormal electro-oculographic findings, and abnormal dark adaptation. The pedigree indicates autosomal dominance as the inheritance pattern.

Adolescent↗
PubMed1993

Familial congenital diaphragmatic hernia: prenatal diagnosis, management, and outcome.

Congenital diaphragmatic hernia (CDH) is a developmental defect of as yet unknown aetiology which accounts for 8 per cent of all major congenital anomalies and is associated with up to 80 per cent mortality despite optimal postnatal treatment. The risk of recurrence of CDH for future sibs after one affected infant is about 2 per cent. A multifactorial/threshold inheritance pattern with an observed high male:female sex ratio is currently favoured for the rare occurrence of familial CDH, although other modes of inheritance have also been described. We report three cases of familial CDH, two of whom were brother and sister sibs and the third was a first cousin, born within 18 months of each other. The diagnosis was by ultrasound and there were several factors predicting a poor outcome. The mortality in this group was 100 per cent. The prenatal diagnosis, treatment options, the unusual genetic aspects, outcome, and the pathology involved are discussed.

Abnormalities, Multiple↗
PubMed1978

Current research in neuro-epidemiology. Some main trends.

Recent epidemiological research has contributed to the understanding of the nature of common neurological disorders like multiple sclerosis, Parkinsonism, and amyotrophic lateral sclerosis. Viral etiology constitutes the most probable environmental factor in multiple sclerosis, but host-related genetic factors are also involved and determine susceptibility. In disorders like Parkinsonism, amyotrophic lateral sclerosis, and epilepsy, heredity seems to play a more important role than earlier believed, and segregation analyses indicate polygenic inheritance patterns. The subacute spongiform encephalopathies fit into a similar concept, and here the hunt for infectious agents has succeeded. Polygenic traits and dominantly inherited disorders seem to aggregate in genetic isolates, as shown through studies from different parts of the world. The reason for this is not quite clear, but selection through assortative matings or other mechanisms may be operating in these populations.

Adolescent↗
PubMed1995

Autosomal dominant rolandic epilepsy and speech dyspraxia: a new syndrome with anticipation.

We describe a family of 9 affected individuals in three generations with nocturnal oro-facio-brachial partial seizures, secondarily generalized partial seizures, and centro-temporal epileptiform discharges, associated with oral and speech dyspraxia and cognitive impairment. The speech disorder was prominent, but differed from that of Landau-Kleffner syndrome and of epilepsy with continuous spike and wave during slow-wave sleep. The electroclinical features of this new syndrome of autosomal dominant rolandic epilepsy resemble those of benign rolandic epilepsy, a common inherited epilepsy of childhood. This family shows clinical anticipation of the seizure disorder, the oral and speech dyspraxia, and cognitive dysfunction, suggesting that the genetic mechanism could be expansion of an unstable triplet repeat. Molecular studies on this syndrome, where the inheritance pattern is clear, could also be relevant to identifying a gene for benign rolandic epilepsy where anticipation does not occur and the mode of inheritance is uncertain.

Adult↗
PubMed1971

Inefficiency of genetic recombination in hybrids between Escherichia coli and Salmonella typhosa.

An Escherichia coli Hfr strain in which three negative chromosomal alleles (leu(-), arg(-), and mtl(-)) were closely linked to three positive alleles (ara(+), rha(+), and xyl(+), respectively) was employed in matings with a Salmonella typhosa recipient. The detected expression of the negative E. coli alleles in S. typhosa hybrids selected for receipt of an associated positive E. coli marker was used to determine the occurrence of haploid S. typhosa recombinants, as distinguished from stable partial diploid hybrids. At the same time, the inheritance patterns and segregation behavior of the positive alleles provided indicators of the occurrence of partial diploid hybrids. Examination of both positive and negative markers inherited by ara(+), rha(+), and xyl(-) selected S. typhosa hybrid classes indicated that relatively short E. coli chromosomal segments (generally about 4 min or less in length) were involved in recombination (haploidy), whereas rather extensive E. coli genetic segments were conserved in the diploid state. S. typhosa hybrids selected for receipt of the ara(+) marker showed a 52% incidence of leu(-) haploidy, which is probably close to being an accurate measure of recombination at the site of the ara(+) allele. S. typhosa hybrids selected for receipt of the rha(+) or xyl(+) markers showed only a 20% incidence of arg(-) or mtl(-) haploidy, respectively, but both of these hybrid classes exhibited a higher incidence of conservation of extensive E. coli diploid segments than did the ara(+) selected class. Remating of haploid S. typhosa hybrids with recombinant xyl(+)mtl(-) or rha(+)arg(-) regions resulted in higher frequencies of hybrid recovery than were observed in the initial matings. However, there was a higher incidence of partial diploidy and a lower incidence of haploidy among the hybrids obtained from these rematings.

Alleles↗
PubMed1998

Evidence for multiple determinants of the body mass index: the National Heart, Lung, and Blood Institute Family Heart Study.

The body mass index (BMI) is a complex phenotype representing the amount of fat mass, lean mass, body build and proportions, and it is likely to be affected by various metabolic processes, hormonal effects, energy intake and expenditure, and interactions within and among these broad categories of etiologic factors. Nonetheless, several previous studies have reported evidence for major gene segregation for the BMI in various populations. Data on a random sample of Caucasian families participating in the National Heart, Lung, and Blood Institute (NHLBI) Family Heart Study were analyzed to document the extent of familial resemblance and to investigate whether a similar monogenic inheritance pattern could be detected. Genetic analysis was carried out on age- and sex-adjusted BMI values. Familial correlations were significant implying a maximal heritability, including all genetic and environmentally inherited additive factors, of 41% to 59%. Segregation analysis revealed the presence of two maximum likelihood solutions, one characterized as a recessive Mendelian gene and the other as a major effect with an ambiguous transmission pattern. The presence of two such solutions is consistent with detection of two separate factors, each influencing the BMI distribution in a substantive manner. The evidence also supports a multifactorial background for BMI and suggests that the frequencies of these two factors, one of which appears to be a gene, may vary among diverse populations in the United States.

Body Mass Index↗
PubMed1994

Cerebellar ataxia, dystonia, and tremor within a family: variable phenotypes of a single genetic disorder?

We report a non-Jewish, Anglo-Saxon, American family, in which one sibling has dystonia, a second has cerebellar ataxia, and a third has a combination of dystonia and ataxia. All three siblings have pyramidal signs. Their mother and maternal uncle have tremor, and their maternal grandmother may have had a neurodegenerative disorder. Although the inheritance pattern is uncertain, this may represent phenotypic variability resulting from a single gene mutation. The multiple phenotypes within this family do not fit any known inherited neurodegenerative or metabolic disorder.

Adult↗
PubMed1986

X-linked ichthyosis, due to steroid sulphatase deficiency, associated with Kallmann syndrome (hypogonadotropic hypogonadism and anosmia): linkage relationships with Xg and cloned DNA sequences from the distal short arm of the X chromosome.

We report a large Italian pedigree in which five out of six males are affected by a syndrome, following an X-linked inheritance pattern, characterized by ichthyosis, hypogonadotropic hypogonadism, and anosmia. The concurrence of features of X-linked ichthyosis (XLI) with those of Kallmann syndrome, another disease often inherited as an X-linked trait, prompted us to perform biochemical, cytogenetic, and molecular studies in relation to the short arm of the X chromosome (Xp). Steroid sulphatase (STS) activity was found to be completely deficient in all affected members of the family. Prometaphase chromosome analyses of two obligate heterozygous women and one affected male showed normal karyotypes. Xg blood group antigen analysis and molecular studies employing cloned DNA sequences from the distal segment of the Xp (probes RC8, 782, dic56, and M1A), did not provide evidence for deletions or rearrangements of the X chromosome. The linkage analysis showed no crossovers between the disease, Xg, and DXS143, the locus defined by probe dic56, thus suggesting the possibility of a linkage between these two markers of the distal segment of Xp and the X-linked ichthyosis, hypogonadism, and anosmia syndrome.

Adolescent↗