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PubMed1986

A strategy for multipoint ordering: example of the 11p markers.

The complete likelihood analysis is required to obtain the evidence for the gene order. Since the number of candidate orders increases rapidly with the number of loci and the complete analysis requires considerable computer time, a method for rapidly screening order is required. To this end, we used the program MAP83 for the initial investigation of order. This method provided a subset of orders to be further investigated by the complete likelihood method. We used PAP for these subsequent analyses. The advantage of algorithms such as MAP83 is that the basic unit of analysis is the set of pairwise LOD scores which are routinely calculated at the beginning of a linkage analysis. However, the magnitude of the log likelihood differences between orders can only be suggestive for two reasons. First, the usual assumptions for MAP83 regarding independence of the recombination fraction estimate are not met by these data and, therefore, no attempt can be made to interpret the log likelihood differences statistically. Secondly, pairwise information precludes identifying the specific inheritance pattern of each gamete, thus the information content of obligatory multiple recombinants is lost. For example, the order HBBC-ADJ-HRAS1-INS requires five double recombinants for the Utah data while the order HBBC-ADJ-INS- HRAS1 does not require any (White et al, 1985). The support for the former order over the latter is a log likelihood difference of 3.73 for the complete likelihood analysis when the HBBC locus is ignored.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosome Mapping↗
PubMed1999

Performance of the nonparametric linkage analysis using GENEHUNTER for a complicated genetic disease.

The nonparametric linkage (NPL) analysis of the GENEHUNTER program was applied to one set of the simulated data of Problem 2, GAW11. We conducted a straightforward screening of the genome to evaluate the performance of the NPL test, with respect to its ability to detect linkage on specific disease loci. Our findings indicate that disease genes were detected with relatively good power, despite the presence of a complex inheritance pattern. We found that the NPL test varies depending on penetrance rates and gene frequencies, however, we conclude that it is a useful tool for linkage analysis.

Alleles↗
PubMedDate not supplied

Familial osteodysplasia.

A family with characteristics that have striking similarities to the syndrome of familial osteodysplasia is reported. The inheritance pattern appears to be autosomal dominant. The typical facies has a lack of vertical facial development and a functional prognathism caused by overclosure of the mandible and opening of the gonial angle. Midfacial hypoplasia and a pointed chin are characteristic. Alveolar and sutural bone growth in the face is diminished and associated with partial dental agenesis. Variable cranial digital markings and possible synostosis are also seen. These typical facial changes are associated with other bony and systemic abnormalities. The long bones have a flask shape and occasionally have increased cortical thickness. The superior pubic ramus is often thin and scoliosis is common. The dermatoglyphic pattern demostrates a distal triradius and small whorl abnormalities. The most significant laboratory values are an increased erythrocyte sedimentation rate and C3 complement found on the erythrocytes. The plasma fibrinogen level was low in all family members.

Adult↗
PubMed1995

Characterization of germline mutations of the gene encoding Bruton's tyrosine kinase in families with X-linked agammaglobulinemia.

Bruton's tyrosine kinase (Btk) has been identified as the protein responsible for the primary immunodeficiency X-linked agammaglobulinemia (XLA) and has been described as a new member of Src-related cytoplasmic protein tyrosine kinases. We have recently characterized the structure of the entire gene encoding Btk and developed a polymerase chain reaction (PCR)-based assay to detect germline mutations within it. In this report we describe six mutations, five of which are novel, of the Btk gene in patients with XLA and demonstrate the inheritance pattern of the defect within the families of the affected individuals. The mutations found include two nonsense and two missense mutations, a single base deletion at an intron acceptor splice site, and a 16-bp insertion. A single strand conformation polymorphism was also found in the 5' end of intron 8 with the same assay. This technique has provided a powerful tool for direct analysis of the Btk gene for the diagnosis of XLA and carrier detection. The identification of new mutations may eventually reveal the role of Btk in the signaling pathways involved in B-cell development.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed2003

Chorea-acanthocytosis: clinical and genetic findings in three families from the Arabian peninsula.

Chorea-acanthocytosis is a rare autosomal recessive disorder. Its characteristics are orofacial dyskinesia, hyporeflexia, seizures, aberrant behavior, atrophy of the caudate and putamen, and acanthocytes in the blood with a normal level of lipoproteins. We describe three families with chorea-acanthocytosis. The inheritance pattern was recessive and the average age at onset was 27 years (range, 18-35 years). The presenting symptoms were seizures, aberrant behaviour, chorea, tics, and/or abnormal gait. Phase-contrast and electron microscopy examinations of blood showed 10 to 40% acanthocytes. The lipid profile was normal except that, in one family, no prebetalipoprotein bands corresponding to the fraction of very low-density lipoprotein were seen in high-resolution lipoprotein electrophoresis. Magnetic resonance imaging of the brain showed marked atrophy in the caudate and putamen; 18-fluorodeoxyglucose positron emission tomography scan showed hypometabolism in the striatum. In all three families, the disease was linked to a 6-cM region of chromosome 9q21 flanked by the recombinant markers GATA 89a11 and D9S1843. This finding strongly suggests the involvement of a single locus for this syndrome. Three different homozygous mutations of this gene have been identified. Although the clinical presentation was variable, the genetic studies on these three Saudi Arabian families with chorea-acanthocytosis provide strong evidence for a genetic locus for chorea-acanthocytosis at chromosome 9q21.

Acanthocytes↗
PubMed2001

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17): PPND family. A longitudinal videotape demonstration.

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17), characterized by an autosomal dominant inheritance pattern, has recently been recognized as a distinct entity that can display a confusingly broad clinical phenotype. The pallido-ponto-nigral degeneration (PPND) variant is the prototypical example of the parkinsonism-predominant pattern of FTDP-17. A longitudinal videotape demonstration of the clinical progression of this entity in a single individual, along with brief videotape segments from three additional affected individuals, is presented in order to facilitate recognition of this disorder.

Adult↗
PubMed1993

Adult onset familial cervical dystonia: report of a family including monozygotic twins.

We report the first family with adult onset cervical dystonia in which monozygotic twins and multiple family members are affected. In this family, the disease exhibits an autosomal dominant inheritance pattern, and all affected members have only cervical dystonia. Five members have definite cervical dystonia, and five others have possible cervical dystonia. Although identical genotypically, the twins demonstrate some phenotypic variation. Despite long follow-up, no family members have shown progression from focal to generalized dystonia. This family may prove valuable in identifying a gene locus for cervical dystonia and hence determine whether a single gene locus exists for hereditable focal dystonia and generalized dystonia.

Adult↗
PubMed1997

Familial cortical myoclonic tremor as a unique form of cortical reflex myoclonus.

Previously it was reported that some patients with tremor had the same electrophysiological findings as those seen in patients with cortical reflex myoclonus, and consequently the tremor was named "cortical tremor." In the present study, we examined six patients from three families with cortical tremor of relatively late onset. The inheritance pattern of cortical tremor was compatible with autosomal dominant trait. Those patients had relatively rhythmic involuntary movements (tremor) in the distal upper and lower limbs, especially during posture and/or fine movements. There was no cerebellar ataxia or dementia, and fits of loss of consciousness occurred only infrequently. Electrophysiologically, they had generalized spikes on electroencephalogram (EEG), giant cortical components of somatosensory evoked potential, an enhanced long-loop reflex (C-reflex), and cortical spikes preceding the rhythmic jerk demonstrable by the jerk-locked back averaging method, thus fulfilling the criteria of cortical reflex myoclonus. Furthermore, they had slow negative EEG shift starting 1-2 s prior to voluntary movements, suggesting that, as opposed to the conventional form of progressive myoclonus epilepsy (PME), the cerebellar efferent input to the motor cortices was normal. These clinical and electrophysiological pictures are distinct from those of familial essential tremor, familial essential myoclonus, or the conventional form of PME, and the term "familial cortical myoclonic tremor" will represent the clinical and electrophysiological features of this unique entity most appropriately.

Adult↗
PubMed2002

Genetic basis of Rett syndrome.

The origin of Rett syndrome has long been debated, but several observations have suggested an X-linked dominant inheritance pattern. We and others have pursued an exclusion-mapping strategy using DNA from a small number of familial Rett syndrome cases. This work resulted in the narrowing of the region likely to harbor the mutated gene to Xq27.3-Xqter. After systematic exclusion of several candidate genes, we discovered mutations in MECP2, the gene that encodes the transcriptional repressor, methyl-CpG-binding protein 2. Since then, nonsense, missense, or frameshift mutations have been found in at least 80% of girls affected with classic Rett syndrome. Sixty-four percent of mutations are recurrent C > T transitions at eight CpG dinucleotides mutation hotspots, while the C-terminal region of the gene is prone to recurrent multinucleotide deletions (11%). Most mutations are predicted to result in total or partial loss of function of MeCP2. There is no clear correlation between the type and position of the mutation and the phenotypic features of classic and variant Rett syndrome patients, and XCI appears to be a major determinant of phenotypic severity. Further research focuses on the pathogenic consequences of these mutations along the hypothesis of loss of transcriptional repression of a small number of genes that are essential for neuronal function in the maturing brain.

Chromosomal Proteins, Non-Histone↗
PubMed2001

Mitochondrial defects in neurodegenerative disease.

Over the past 12 years, a wide variety of neurodegenerative diseases has been linked to mutations in mitochondrial genes located in either the mitochondrial DNA (mtDNA) or the nuclear DNA (nDNA). These disorders encompass an array of unorthodox inheritance patterns and a plethora of symptoms ranging from lethal neonatal multi-symptom disorders to later onset myopathies, cardiomyopathies, movement disorders, and dementias. The bases for the genetic and phenotypic variability of mitochondrial diseases lie in the multiplicity of the mitochondria genes dispersed across the human genome and the variety of cellular pathways and functions in which the mitochondria play a central role.

Aging↗
PubMedDate not supplied

A new variant of late-onset myophosphorylase deficiency.

McArdle disease classically presents in childhood or adolescence. Rarely does it become symptomatic for the first time in late adulthood, with the onset of progressive muscle wasting and weakness. Our patient is unusual in that despite a life of physical vigor, she developed immobilizing cramps, stiffness, and muscle swelling abruptly at age 60. She had no previous symptoms of muscle disease. The diagnosis was indicated by the ischemic forearm test, which produced muscle contracture and no rise in venous lactate levels, and confirmed by histochemical, electrophoretic, and biochemical studies that showed complete absence of myophosphorylase. This case defines a new variant of the late-onset type and raises important questions about compensatory mechanisms, inheritance patterns, and etiological factors in myophosphorylase deficiency.

Age Factors↗
PubMed1989

The role of collagen crosslinking in the increased stiffness of avian dystrophic muscle.

The resting tension and stiffness in the range of sarcomere lengths 2.4-3.6 microns were studied in highly inbred normal and dystrophic chicken pectoral muscle bundles, and the results were compared with the collagen content and the extent of crosslinkage of the collagen. All parameters increased in the order normal homozygote (003/003) less than heterozygote (003/433) less than dystrophic homozygote (433/433) chickens, with the data from the heterozygotes being halfway between the two homozygotes, thus exhibiting a semi-dominant inheritance pattern. In separate experiments, lathyrism was induced by treating normal (412/412) and dystrophic (413/413) chickens with alpha-acetoaminonitrile, an inhibitor of lysyl oxydase, the enzyme responsible for the initiation of collagen crosslinkage formation. These experiments showed that the tension and stiffness in response to passive stretch did not change with lathyrism in normal muscles, whereas the tension and stiffness decreased significantly with lathyrism in dystrophic muscles. The collagen content did not change with lathryrism in both normal and dystrophic muscles. These results indicate that the increased content of collagen crosslinkages is the basis for the increased resting tension and stiffness in the dystrophic muscles of the chicken, and that the effects can be reversed by treatment with an inhibitor of collagen crosslinkage formation.

Animals↗
PubMed1992

Atelosteogenesis type II: sonographic and radiological correlation.

Atelosteogenesis type II is a lethal chondrodysplasia characterized by severe micromelia, spinal abnormalities, talipes equinovarus, and abducted thumbs and toes. We present a case diagnosed at 21 weeks of gestation in which antenatal sonographic and post-mortem radiological findings were correlated. The patient had a recurrence of this disorder in a subsequent pregnancy which was terminated at 15 weeks, supporting previous reports of an autosomal recessive inheritance pattern. The feasibility of diagnosing the following morphological features by prenatal ultrasonography is demonstrated: coronal clefts of the vertebral bodies, metaphyseal and epiphyseal abnormalities, spinal deviations such as cervical kyphosis and a horizontal sacrum, additional ossification centres in the pelvis, and preaxial deviation of the thumbs and toes. The differential diagnosis of this disorder from other skeletal dysplasias with similar features is discussed.

Abnormalities, Multiple↗
PubMed2001

Familial orofaciodigital syndrome type I revealed by ultrasound prenatal diagnosis of porencephaly.

Porencephaly is a rare central nervous system (CNS) abnormality that can be caused by an intraparenchymal destructive process or a developmental defect. Here we report on a prenatal ultrasound diagnosis of complex CNS abnormalities including agenesis of the corpus callosum, agenesis of the cerebellar vermis, bilateral hydrocephaly, and bilateral porencephaly in fetus at 33 weeks' gestation. The diagnosis of familial orofaciodigital syndrome type I (OFD I) was raised after fetal autopsy, clinical examination of the family, and the X-linked dominant inheritance pattern. This is the fourth report of porencephaly in association with OFD I. We discuss the difficulties in genetic counselling since OFD I shows variable expressivity of the phenotypic features. Furthermore, we emphasize the importance of a detailed ultrasound examination after a prenatal diagnosis of porencephaly.

Brain↗
PubMed1993

Structural heterogeneity of Caucasian N-acetyltransferase at the NAT1 gene locus.

The human N-acetylation polymorphism is a genetic trait phenotypically reflected by differences in N-acetyltransferase (NAT) activity with therapeutic agents (rapid and slow acetylation), but a genetic invariability in N-acetylation of some arylamine drugs is also known. There are two highly similar human NAT genes: NAT1 is thought to encode a genetically invariant protein, whereas NAT2 has conclusively been shown to represent a polymorphic locus. This study demonstrates the presence of discrete NAT1 structural variants among Caucasians. These were detected by direct sequencing of 1.6-kilobase NAT1 fragments generated by the polymerase chain reaction with liver and leukocyte DNA from 13 subjects of established acetylator phenotype and NAT2 genotype. A prominent alteration in one of the variants was obliteration of the consensus polyadenylation signal (AATAAA-->AAAAAA). Several mutations were discernible in all regions of the second variant allele, including silent (codon 153) and nonsilent (Ser-214-->Ala) substitutions in the coding region and deletion of nine bases from an AT-rich segment in the 3' untranslated region. One-half of the unrelated subjects were either homozygous or heterozygous for the mutant NAT1 alleles, both of which obeyed a Mendelian inheritance pattern. These novel results unambiguously show that human NAT1, like NAT2, is a polymorphic locus.

Acetylation↗
PubMed1996

Normal mitochondrial DNA and respiratory chain activity in familial dysautonomia fibroblasts.

Familial dysautonomia (FD), an autosomal recessive disease mapped to chromosome 9q31, is a sensory and autonomic neuropathy of unknown etiology. We have previously reported light microscopic pleiomorphic changes in cells suggestive of altered plasma membranes, an increase in globotriaosylceramide (Gb3), reflected by an increase in Gb3 on the surface of the plasma membrane, and a decrease in the rate and amount of ganglioside synthesized. In unrelated studies, we demonstrated that storage of glycospingolipids (GSL) is deleterious to mitochondrial function. Recently, mitochondrial dysfunction has been associated with neurodegenerative disease, superimposed on an autosomal inheritance pattern. We have now probed Southern blots of total FD fibroblast DNA, digested with BamHI, EcoRII, and/or PvuII, with purified placental 32P-labeled mitochondrial DNA. The sizes of all FD mitochondrial DNAs were normal (16,569 bp), some containing previously identified BamHI polymorphisms. Lactate/pyruvate ratios, and activities of Complexes II and III, matched those of control cells. Electron microscopy revealed morphologically normal mitochondria, in conjunction with a normal oxidative state, determined using the redox dyes Mito Tracker CMXR and CMXR-H2 and fluorescence microscopy. We conclude that mitochondrial dysfunction, due to GSL accumulation, changes in mitochondrial DNA, or mutation of a chromosome 9q gene involved in mitochondrial function, is neither a primary nor a secondary cause of FD, as determined by a study of FD fibroblasts.

Blotting, Southern↗
PubMed1994

The centrosome and its mode of inheritance: the reduction of the centrosome during gametogenesis and its restoration during fertilization.

Neither the restoration of the centrosome during fertilization nor its reduction during gametogenesis is fully understood, but both are pivotal events in development. During each somatic cell cycle, the chromosomes, cytoplasm, and centrosomes duplicate in interphase, and all three split in two during each cell division. While it has long been recognized that both the sperm and the egg contribute equal haploid genomes during fertilization and that the vast majority of the cytoplasm is contributed by the egg, the relative contributions of the centrosome by each gamete are still in question. This article explores centrosome inheritance patterns and considers nine integral and secondarily derived activities of the centrosome. Boveri once hypothesized that "The ripe egg possesses all of the elements necessary for development save an active division-center. The sperm, on the other hand, possesses such a center but lacks the protoplasmic substratum in which to operate. In this respect the egg and sperm are complementary structures; their union in syngamy thus restores to each the missing element necessary to further development." This article reviews the evidence gathered from 11 experimental strategies used to test this theory. While the majority of these approaches supports the hypothesis that the sperm introduces the centrosome at fertilization, the pattern did not reveal itself as universal, since parthenogenesis occurs in nature and can be induced artificially, since centrosome and centriole form de novo in extracts from unfertilized eggs and since the centrosome is derived from maternal sources during fertilization in some systems--notably, in mice. Models of the centrosome are proposed, along with speculative mechanisms which might lead to the cloaking of the reproducing element of the maternal centrosome during oogenesis and the retention of this structure by the paternal centrosome during spermatogenesis. Proteins essential for microtubule nucleation, like gamma-tubulin, are retained in the cytoplasm during oogenesis, but are largely lost during spermatogenesis. It is further postulated that the restoration of the zygotic centrosome at fertilization requires the attraction of maternal centrosomal components (in particular, gamma-tubulin and the 25S "gamma-some" particle) to the paternal reproducing element; this, along with post-translational modifications (including phosphorylation, disulfide reduction, and calcium ion binding), creates a functional zygote centrosome by blending both maternal and paternal constituents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗