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PubMed2004

Homozygosity mapping of a third Joubert syndrome locus to 6q23.

BACKGROUND: Joubert syndrome (JS) is a recessively inherited disorder characterised by hypotonia at birth and developmental delay, followed by truncal ataxia and cognitive impairment, characteristic neuroimaging findings (cerebellar vermis hypoplasia, "molar tooth sign") and suggestive facial features. JS is clinically heterogeneous with some patients presenting with breathing abnormalities in the neonatal period, oculomotor apraxia, retinal dystrophy, retinal coloboma, ptosis, hexadactyly, and nephronophtisis or cystic dysplastic kidneys. JS is also genetically heterogeneous, with two known loci, on 9q34 (JBTS1) and 11p11-q12 (CORS2), representing only a fraction of cases. METHODS: A large consanguineous Joubert family (five affected) was analysed for linkage with a marker set covering the entire genome and 16 smaller families were subsequently tested for candidate loci. RESULTS: We report here the identification of a third locus in 6q23 (JBTS3) from the study of two consanguineous families. LOD score calculation, including the consanguinity loops, gave a maximum value of 4.1 and 2.3 at q = 0 for the two families, respectively. CONCLUSIONS: Linkage between the disease and the D6S1620-D6S1699 haplotype spanning a 13.1 cM interval is demonstrated. Genotype-phenotype studies indicate that, unlike CORS2, JBTS3 appears not to be associated with renal dysfunction.

Abnormalities, Multiple↗

PubMed1998

PCR based mutation screening of the laminin alpha2 chain gene (LAMA2): application to prenatal diagnosis and search for founder effects in congenital muscular dystrophy.

Classical congenital muscular dystrophy with merosin deficiency is caused by mutations in the laminin alpha2 chain gene (LAMA2). Extended sequencing of the introns flanking the 64 LAMA2 exons was carried out and, based on these sequences, oligonucleotide primers were designed to amplify the coding region of each exon separately. By PCR-SSCP analysis, we identified eight new mutations in nine families originating from various countries. All induced a premature truncation of the protein, either in the short arm or in the globular C-terminal domain. A 2 bp deletion in exon 13, 2098delAG, was found in three French non-consanguineous families and a nonsense mutation of exon 20, Cys967stop, in two other non-consanguineous families originating from Italy. Determination of rare intragenic polymorphisms permitted us to show evidence of founder effects for these two mutations suggesting a remote degree of consanguinity between the families. Other, more frequent polymorphisms, G to A 1905 (exon 12), A to G 2848 (exon 19), A to G 5551 (exon 37), and G to A 6286 (exon 42), were used as intragenic markers for prenatal diagnosis. This study provides valuable methods for determining the molecular defects in LAMA2 causing merosin deficient congenital muscular dystrophy.

Child↗

PubMed1998

A comparison of disease and gene frequencies of inborn errors of metabolism among different ethnic groups in the West Midlands, UK.

OBJECTIVE: To assess birth and gene frequencies of specific autosomal recessively inborn errors of metabolism (IEM) within different ethnic groups. DESIGN: Retrospective study in a regional centre for investigation and treatment of IEM. SUBJECTS: All children born within the West Midlands NHS Region, UK, during the decade immediately preceding the 1991 National Census. METHODS: Birth frequencies for individual IEM were calculated separately for the main ethnic groups in the West Midlands using data from the West Midlands Neonatal Screening Programme, the regional register of IEM patients, and population frequencies from the National Census. Gene frequencies were calculated using previously documented observations on parental consanguinity rates and inbreeding coefficients. RESULTS: The overall incidence of recorded IEM was tenfold higher among Pakistanis compared to white children (1:318 v 1:3760), whereas only one AfroCaribbean child was identified (incidence 1:16 887). Tyrosinaemia type 1, cystinosis, mucopolysaccharidosis type 1, non-ketotic hyperglycinaemia, and hyperchylomicronaemia all occurred more frequently among Pakistanis. An increased gene frequency was only confirmed for tyrosinaemia. The incidence of phenylketonuria was similar in Pakistani and white children (1:14 452 v 1:12 611), but the gene frequency was significantly lower in Pakistanis (1:713 v 1:112). These results illustrate the interplay between gene frequency and parental consanguinity in determining disease frequencies in different populations, and indicate anticipated disease frequencies in the absence of consanguineous marriage. These figures have implications for the organisation of services for management of inborn errors, for genetic counselling, and for the assessment of gene flow in world populations.

Ethnicity↗

PubMed1994

Mapping of Friedreich's ataxia locus by identification of recombination events in patients homozygous by descent.

The Friedreich's ataxia locus (FRDA) maps on chromosome 9q13. Genetic data, obtained from a small number of recombination events, indicated that the FRDA locus might be located centromeric to the D9S15/D9S5 linkage group, the most probable order being cen-FRDA-D9S5-D9S111-D9S15-D9S110-qter. Recently, new centromeric markers have been reported. Analysis of these markers allowed us to localize the recombination breakpoint in some of the recombinant families. However, only one proximal recombination has been found with these markers. To increase the genetic information from FRDA families, we have analyzed the centromeric markers FR1, FR2, FR7, FR8, and FR5 in patients homozygous by descent. These were ascertained because parents were consanguineous or because they were homozygous for the entire haplotype D9S15 or D9S111-D9S5-D9S411E-D9S202. Haplotype divergence for, at least, two contiguous markers was observed in two patients homozygous for the core D9S111-FR2 haplotype and in one third-degree consanguineous family homozygous for haplotype D9S411E-FR5. Interpretation of divergence as the result of ancient meiotic crossovers allowed the definition of three new recombination events which place the FRDA locus within the interval defined by markers D9S411E and FR8. A consanguineous family with first-cousin parents showed homozygosity only at D9S202 and FR2. Further investigations are needed to discern whether two different mutations are segregating in the family or whether two recombinations, one distal and one proximal, have taken place.

Biomarkers↗

PubMed1999

Cancers in children younger than age 16 years in Kenya.

OBJECTIVE: To determine the number of cancers seen in six months in children aged below sixteen years and to look for any associations with breastfeeding, parental ages, smoking, water availability and consanguinity. DESIGN: Prospective case study from June 1997 through December 1997. SETTING: Seven provincial hospitals and Kenyatta National Referral Hospital. SUBJECTS: Both sexes with tissue proven malignancy. INTERVENTIONS: By obtaining clinical information, and laboratory evaluatory results. MAIN OUTCOME MEASURES: Proportions of vital statistics, anatomic site, stage and histology of cancer, vaccination, breastfeeding, congenital abnormality, parental vital statistics, education, smoking, water availability status and consanguinity. RESULTS: One hundred and fifty seven cases were evaluated. Male to female (M:F) ratio was 1.5:1. Mean ages: patients 6.5, fathers 36.6, mothers 31.1 years. Histologic types were: Burkitt's lymphoma (BL) 45%, nephroblastoma 14%, Hodgkin's lymphoma 9.5%, acute lymphocytic leukaemia 7.6%, retinoblastoma 5.7%, acute myeloid leukaemia 5.1%. The age distribution was as follows: 0-5 years, 46.5%, 6-10, 39.5% and 11-16 years 14%. The birth places of the children were as follows: Nyanza 25%, Central 21%, Eastern 16%, Western 13%, Rift Valley 9%, Coast 8%, Nairobi 8% and North Eastern had less than one per cent. The ethnic distribution was; Luo 25%, Kikuyu 22%, Luhya 13%, Kamba 10%, Coastal 6%, Kalenjin 6%, others 19%. Fifty per cent of the cases studied were breastfed for over six months, 34% for 3-6 months, five per cent less than three months and eleven per cent were not breastfed. Eighty five per cent of the cases received complete vaccination. The modal number of siblings was four and only 49% of parents received formal education. No consanguinity was noted in the studied population. The abdomen and jaw were main anatomic sites involved by the tumours. CONCLUSION: This study showed that the commonest childhood tumour is Burkitt's lymphoma and nephroblastoma is the commonest solid tumour. While the results demonstrate geographic and ethnic variations, other factors studied do not appear to influence the characteristics of cancers in the cases investigated.

Adolescent↗

PubMed1999

[Two cases of sporadic juvenile Parkinson's disease caused by homozygous deletion of Parkin gene].

Parkin gene, which is one of the causes of familial Parkinson's disease, was cloned in 1998, and it was found that mutations of this gene induces familial Parkinson's disease of autosomal recessive form (AR-JP). Clinical studies have revealed that almost cases of AR-JP are consanguineous or hereditary. However, AR-JP may also be caused by marriage between two carriers. We therefore investigated the existence of a homozygous deletion in the parkin gene in 10 patients with juvenile Parkinson's disease with the onset of age younger than 40 years without consanguinity or heredity. A large delection of the gene was found in 2 of the 10 patients with sporadic Parkinson's disease, and both of these deletion were exon 4. The present study clearly suggests that juvenile Parkinson's disease in Japan may be caused by abnormalities in parkin gene regardless of family history or consanguinity.

Age of Onset↗

PubMed1975

[Inbreeding in the population and the spread of schizophrenia in one of the rural regions of Azerbaijan].

The investigation was carried out in Pushkin region of Azerbaijan SSR. The coefficient of inbreeding was found to be 0,01306 and 0,01142 in 2 typical villages; the frequency of consanguineous marriage in both villages was 30%. The occurence of consanguineous marriage is explained by a little migration of the population, large families and a stability of marriage traditions. An increased frequency of parental consanguinities of sporadic schizophrenic patients in comparison with the average one was found. This indicates the determination of some cases by rare recessive genes.

Azerbaijan↗

PubMed1975

[Characteristics of inbreeding of the population and distribution of schizophrenia in one of the rural regions of Azerbaijan].

The investigation was carried out in Pushkin region of Azerbaijan SSR. The coefficient of inbreeding was found to be 0,01306 and 0,01142 in 2 typical villages; the frequency of consanguineous marriage in both villages was 30%. The occurrence of consanguineous marriage is explained by a little migration of the population, large families and a stability of marriage traditions. An increased frequency of parental consanguinities of sporadic schizophrenic patients in comparison with the average one was found. This indicates the determination of somes cases by rare recessive genes.

Azerbaijan↗

PubMed2004

[Quantitative analysis of SMN gene copies in spinal muscular atrophy].

OBJECTIVE: To study the genetic basis in the patients with clinical diagnosis of spinal muscular atrophy(SMA) but without survival motor neuron telomeric copy (SMN-T) deletion; the relationship between the SMN-C (centromeric) copies and the phenotype; and the distribution of SMN-C and SMN-T copies in the SMA patients, the carriers and the controls. METHODS: Quantitative PCR analysis of SMN-T and SMN-C copies were carried out in 45 patients, 25 consanguineous and 33 control individuals. The patients were identified by clinical manifestation and muscular pathology. Two internal standards of SMN-T and cystic fibrosis transmembrane conductance regulator (CFTR) were constructed. Nonradioactive and nonfluorescence-labelling competitive PCR were used. The numbers of SMN-T and SMN-C copies were determined by calculating the ratios of SMN-T/CFTR and SMN-C/CFTR. RESULTS: Quantitation of SMN-T gene copies in SMA patients revealed that nine cases of type I-III were homozygously deleted. Two cases of type III had only one copy and four cases of type III had two copies. SMA IV and other type cases had two copies. Nine cases of consanguineous individuals had one copy, but other 16 had two copies. All of the normal individuals had two copies. Analysis of SMN-C copies showed that SMA I had < or = 2 copies, II-III had < or = 3 copies, SMA IV and others had 0-3 copies, the consanguineous individuals and normal individuals had 0-3 copies. CONCLUSION: The number of copies determined by PCR quantitative assay of SMN-T is in accordance with the result of PCR qualitative assay of homozygous deletion. Quantitative assay of the number of copies can find out the cases and the carriers of heterozygous deletion. The SMA phenotype is related to the number of copies of SMN-C; the smaller the number of copies the patient has, the severer the patient's phenotype will be. The pathogenesis of SMA IV and other types of SMA may not relate to SMN gene.

Cyclic AMP Response Element-Binding Protein↗

PubMed1992

Xeroderma pigmentosum variant with multisystem involvement.

BACKGROUND: Xeroderma pigmentosum (XP) is a hereditary disorder characterized by recessive inheritance and elevated rates of skin carcinogenesis. There are seven complementation groups (A through G) for which the genetic defect results in a failure to repair DNA damage from UV light and sunlight; one group, the variant, fails to replicate UV-damaged DNA correctly. Patients in XP groups A, B, D, and G have associated neurologic problems, the most severe being known as the DeSanctis-Cacchione syndrome. OBSERVATIONS: We describe a patient with XP from consanguineous parents who has severe multisystem involvement similar to that of the DeSanctis-Cacchione syndrome. Extensive laboratory investigation showed that cells from this patient exhibit DNA replication after irradiation with UV light that is characteristic of the XP variant. The cells also show normal sensitivity to UV light and normal excision repair, consistent with XP variant classification. The presence of the neurologic symptoms is quite unusual in an XP variant. CONCLUSION: Our patient clearly fits into the XP variant category based on normal survival, caffeine toxic reaction, photoproduct excision and repair, and the deficient replication of UV-damaged DNA. This patient seems to be rare, however, among XP variants in displaying severe neurologic symptoms. Because of the consanguineous parents, the possibility that some of this patient's findings are from non-XP-related abnormalities must also be entertained. However, other consanguineous patients with XP variant, eg, XPIOCA, have been described who do not show neurologic abnormalities. In view of the difficulty of defining an XP group from clinical symptoms alone, we urge the term xeroderma pigmentosum variant be used only in the context of the laboratory studies of patients with XP that contain normal repair but deficient semiconservative replication of UV-damaged DNA.

Cell Survival↗

PubMed1991

[DNA diagnosis in endocrinological disease--pituitary disease].

Endocrine disorders have long been diagnosed by symptoms, before hormones were able to be measured by immunoassays. Recently, as molecular biological methods developed, DNA diagnosis has become available in many diseases including endocrine disorders. We present here DNA diagnosis in connection with anterior pituitary hormones. Our studies on thyrotropin (TSH) producing pituitary adenomas showed that TSH beta-subunit mRNAs of the adenomas were the same as those from normal pituitary tissues. Congenital isolated TSH deficiency is rare disease causing hypothyroidism including cretinism, severe mental and growth retardation. We have studied 3 families with consanguineous marriage and 2 families which were descendants of closed colonies. The molecular pathogenesis were elucidated in the cases of 3 Japanese families with consanguineous marriage. They had a same missense mutation in the 2nd exon of the TSH beta-subunit gene which made a restriction enzyme site, and could be analyzed either by genomic Southern blot analyses or by restriction enzyme digestion after amplification of genomic DNA by PCR. Congenital deficiency of growth hormone, prolactin, and TSH was first described in Snell dwarf mice. The gene encoding the nuclear factor Pit-1/GHF-1, which transactivates promoters of both growth hormone gene and prolactin gene, was shown to be the cause of Snell dwarf mice. A similar human case arose from a family with consanguineous marriage, and the relation with the pit-1/GHF-1 gene is now under study.

DNA↗

PubMed1989

Immunological investigations in 2 families with progressive diaphyseal dysplasia.

Immunological studies were done in members of 2 families with progressive diaphyseal dysplasia. In one family 10 patients and 5 healthy consanguineous relatives were studied, and in the second family one patient and 4 healthy consanguineous relatives were investigated. Evaluation included serum immunoglobulin and complement levels, peripheral blood mononuclear cell subpopulations and lymphocyte stimulation by mitogens. Immunoglobulin and complement levels were normal. All patients had markedly elevated proportions of OKM1 positive mononuclear cells and some of the healthy consanguineous relatives also exhibited the same abnormality. Proliferative responses of lymphocytes to phytomitogens were generally normal. This abnormality of mononuclear cell subset seems to serve as a marker of the disease and may reflect immune mechanisms involved in this disorder.

Adolescent↗

PubMed1984

Cold reacting anti-nuclear factor (ANF) in families of patients with IgA nephropathy.

The emergence of cold reacting anti-nuclear factor (ANF) in families of patients with IgA nephropathy was examined to determine whether some immunological alterations among family members affect the development of this disease. The procedure for the detection of the cold reacting ANF was reported previously. Fifty-five per cent of sera from 66 relatives of IgA nephropathy 24 patients was found to have the IgM cold reacting antibody. The incidence of ANF in healthy adults was 3%. Both household and non-household consanguineous relatives showed antibody in their sera. Sixty-five per cent of consanguineous relatives who had close household contacts with IgA nephropathy patients showed cold reacting ANF, whereas only 10% of non-consanguineous relatives who had close household contact had this antibody. It is suggested that familial susceptibility or genetic factors, in addition to environmental factors, may be responsible in the development of IgA nephropathy.

Adolescent↗

PubMed2003

Phenotypical features of a Moroccan family with autosomal recessive Charcot-Marie-Tooth disease associated with the S194X mutation in the GDAP1 gene.

BACKGROUND: The first locus for demyelinating autosomal recessive Charcot-Marie-Tooth (ARCMT) disease was identified in 8q13, where mutations in GDAP1 have been found. Mutations in the same gene have been detected in families with axonal ARCMT disease. OBJECTIVE: To determine the clinical, electrophysiologic, and morphologic characteristics of a consanguineous Moroccan family with ARCMT disease associated with the S194X mutation in the GDAP1 gene. METHODS: Four patients from a consanguineous Moroccan family were examined clinically and electrophysiologically. In one patient, a morphometric and ultrastructural study of a peroneal nerve biopsy sample was performed. Mutation in the coding region of the GDAP1 gene was identified by direct sequencing. RESULTS: Neuropathy was evident early in childhood, walking was delayed in one patient, and onset of symptoms occurred before 18 months in the others. The phenotype was severe: foot deformities and disabilities involving the hands and feet developed toward the end of the first decade, followed by involvement of proximal muscles in the lower limbs, leading to loss of autonomy. Electrophysiologic findings were consistent with an axonal form of CMT disease: motor nerve conduction velocities, recordable in one patient only, were greater than 40 m/sec. Sensory nerve action potentials were either abolished or substantially reduced in amplitude. The morphologic data supported the diagnosis of axonal neuropathy, showing a marked reduction in myelinated fibers and signs of axonal regeneration, including frequent pseudo-onion bulb formations. The 4 patients in this family were homozygous for the S194X mutation in the GDAP1 gene. CONCLUSION: Electrophysiologic and pathological findings support the hypothesis of an axonal disorder in this ARCMT family with the S194X mutation in the GDAP1 gene.

Adolescent↗

PubMed1996

Constellation of congenital abnormalities in an infant: a new syndrome or tissue-specific mosaicism for trisomy 18?

A newborn infant born to consanguineous (first cousin) parents was noted to have complex congenital heart defect and minor anomalies suggestive of trisomy 18. Blood lymphocyte and skin fibroblast karyotypes were normal. He died in the neonatal period of postoperative complications. On interphase fluorescence in-situ hybridization (FISH) using autopsy specimens, a significant number of cells in the liver (17%) were trisomic for chromosome 18, compared to normal control liver tissue. However, interphase FISH analyses of blood lymphocytes, skin fibroblasts, and kidney tissue were normal. It is our opinion that this apparent mosaicism for trisomy 18 in the patient's liver may be spurious, though it brings into focus the issue of possible tissue/organ-specific mosaicism. The anomalies in this infant do not resemble a previously described malformation syndrome. Parental consanguinity raises the possibility that this represents a new autosomal recessive malformation syndrome.

Abnormalities, Multiple↗

PubMed1996

Aprosencephaly and cerebellar dysgenesis in sibs.

Aprosencephaly is a rare, lethal malformation sequence of the central nervous system that has been attributed to a postneuralation encephaloclastic process. We describe autopsy findings consistent with aprosencephaly in 2 fetuses conceived from a consanguineous mating (first cousins). Both showed anencephalic manifestations; however, the crania were intact, with fused sutures. The neuropathologic findings were essentially identical. Each fetus had complete absence of the telecephalon and pyramidal tracts, rudimentary diencephalic and mesencephalic structures, primitive cerebellar hemispheres, posterolateral clusters of primitive neural cells in the medullas suggesting an abnormality of neural migration, a normally-formed spinal cord, and retinal dysplasia within normally-formed globes. In addition, both fetuses manifested a peculiar perivascular mesenchymal proliferation seen only within the central nervous system. The similarity of these cases, coupled with parental consanguinity, suggests a primary malformation in brain development due to the homozygous representation of a mutant allele. We hypothesize that these patients may represent a defect in a gene important in brain development, the nature of which has yet to be elucidated.

Abnormalities, Multiple↗

PubMed1996

Congenital vocal cord paralysis with possible autosomal recessive inheritance: case report and review of the literature.

We describe an infant with congenital vocal cord paralysis born to consanguineous parents. While autosomal dominant and X-linked inheritance have been previously reported in this condition, we conclude that the degree of parental consanguinity in this case strongly suggests autosomal recessive inheritance. Although we cannot exclude X-linked inheritance, evidence from animal studies demonstrates autosomal recessive inheritance and provides a possible molecular basis for congenital vocal cord paralysis.

Adult↗

PubMed2000

A study of contemporary levels and temporal trends in inbreeding in the Tangier Island, Virginia, population using pedigree data and isonymy.

In this study we describe inbreeding in a large pedigree from Tangier Island, Virginia, in which we compare two commonly used methods to estimate inbreeding in humans: pedigree and isonymy (identical surnames of spouses). Genealogical data on 3,512 individuals dating back to 1722 were used. Using the pedigree method, we determined an average inbreeding coefficient (F) of 0.00873 for the community as a whole, and 0.018 for inbred individuals. Analysis of temporal trends showed that inbreeding began around 1800 and peaked at 0.0109 in 1824-1849 and 1875-1899. Thereafter, inbreeding steadily declined to 0.00565 in 1975-1997. Analysis of pedigree structure complexity over time showed that close consanguinity contributes to inbreeding in the earlier cohorts, and remote consanguinity accounts for much of the inbreeding in the later cohorts. The number of common ancestors increases over time, as does the number of paths connecting inbred individuals to these common ancestors. Inbreeding estimates based on the isonymy approach yielded a 2.2-fold higher value of F (0.01945) compared to the pedigree method. Total isonymy estimates over 25-year cohorts overestimated inbreeding values from pedigree data between 1. 5-8-fold. We speculate that the overestimation is probably due to the inability of our data to satisfy the method's assumption of monophyletic origin of each surname. In conclusion, inbreeding in the Tangier Island population is consistent with the isolated nature of its population, and temporal trends reflect patterns in emigration and a breakdown in isolation over time.

Adolescent↗