Genetic services in France.
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Birth Rate↗
Biomedical subjects
M L Briard
Publications and source records attributed to M L Briard.
[Advances in genetics: what benefits children?].
The advent of genetic therapy has raised great hopes, but it is clear that for children and their parents, the primary benefit from recent progress is in the possibility of positive diagnosis and presymptomatic diagnosis allowing more adapted management. For the family, genetic counselling allows well informed family planning and birth of healthy children. For the child to be born, continuing progress in genotypic diagnosis often leads to very delicate questions during the antenatal period, especially since certain diagnoses are still difficult and prognosis less than sure. The wide range of tools in molecular genetics may provide the answer in many situations. The rapid development of genetic tools in developed countries should now raise the question of their use in developing countries. This point might have a particular impact in research on genetic factors and sensibility to frequent infectious diseases such as tuberculosis or malaria. In this case, the aim is not diagnosis but the discovery of genes regulating susceptibility which could lead to pharmaceutical developments. This is undoubtedly a long term objective, but should not be overlooked.
Age Factors↗
[Rise of genetics: what are the benefits for children?].
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Child↗
Increased paternal age in CHARGE association.
The acronym CHARGE refers to a non-random clustering of congenital malformations whose cause remains unknown. Here, we report on a series of 41 patients and find a significant increase in mean paternal age of birth of CHARGE patients (33.7 +/- 8 years) compared with the control population (30.8 +/- 5 years). In contrast, maternal age was not statistically different in patients and controls. These data suggest the possible role of a dominant mutation or, less likely, a subtle chromosomal abnormality in CHARGE association.
Abnormalities, Multiple↗
A gene for Leber's congenital amaurosis maps to chromosome 17p.
Leber's congenital amaurosis (LCA) is an autosomal recessive disease responsible for congenital blindness. It is the most early and severe form of inherited retinopathy and accounts for 5% of all inherited retinal dystrophies. Here we report the first mapping of a gene for LCA to the distal short arm of chromosome 17 by linkage analysis in 15 multiplex families (Zmax = 5.14 at theta = 0.15 for probe AFM070xg5 at the D17S1353 locus). When our sample was split into two groups according to the ethnic origin of the patients we were able to confirm the presence of a gene for LCA on chromosome 17p by both homozygosity mapping and linkage analysis in five families of Maghrebian origin (LCA1, Zmax = 7.21 at theta = 0.01 at the D17S1353 locus), while negative results were found in 10 families of French ancestry. Haplotype analyses supported the placement of LCA1 between loci D17S796 and D17S786 (maximum likelihood estimate for location of the disease gene over the D17S1353 locus). The genetic heterogeneity of LCA will complicate the prenatal detection of this frequent cause of congenital blindness.
Blindness↗
A gene for Hirschsprung disease maps to the proximal long arm of chromosome 10.
Hirschsprung disease (HSCR) is a frequent congenital disorder (1 in 5,000 newborns) of unknown origin characterized by the absence of parasympathetic intrinsic ganglion cells of the hindgut. Taking advantage of a proximal deletion of chromosome 10q (del 10q11.2-q21.2) in a patient with total colonic aganglionosis, and of a high-density genetic map of microsatellite DNA markers, we performed genetic linkage analysis in 15 non-syndromic long-segment and short-segment HSCR families. Multipoint linkage analysis indicated that the most likely location for a HSCR locus is between loci D10S208 and D10S196, suggesting that a dominant gene for HSCR maps to 10q11.2, a region to which other neural crest defects have been mapped.
Base Sequence↗
A gene for Stargardt's disease (fundus flavimaculatus) maps to the short arm of chromosome 1.
Stargardt's disease (fundus flavimaculatus) is one of the most frequent causes of macular degeneration in childhood and accounts for 7% of all retinal dystrophies. It is an autosomal recessive condition characterized by a bilateral loss of central vision occurring at age 7-12 years. Genetic linkage analysis of eight families has assigned the disease locus to chromosome 1p21-p13. Multipoint linkage analysis and haplotype analysis has allowed us to establish the best estimate for location of the gene over the locus D1S435 (maximum lod score of 12.66). Our results are consistent with the genetic homogeneity of this condition.
Child↗
[Prenatal, neonatal and postnatal prevention in cystic fibrosis].
The efficiency of neonatal screening for CF could be improved by associating a molecular analysis to the immunoreactive trypsin test, on the same dried blood's sample. However the interest of such a screening for the patients benefit remains controversial. In most cases, antenatal diagnosis may be performed by a direct search of the mutation(s). However, the impact of antenatal diagnosis on CF's incidence will necessarily be limited if it can only be implemented after the birth of an affected child. Hence the interest of screening programs for the detection of healthy carriers. Carrier's detection does not raise any objection for the relatives of patients. It is still premature to recommend it to be undertaken in the general population.
Cystic Fibrosis↗
Linkage disequilibrium between phenylketonuria and RFLP haplotype 1 at the phenylalanine hydroxylase locus in Portugal.
RFLPs of 36 normal and 41 mutant alleles at the phenylalanine hydroxylase locus were determined in 31 Portuguese kindreds. A total of 14 haplotypes including 10 normal and 7 mutant alleles were observed. Almost 75% of all mutant alleles were confined within only two haplotypes, namely haplotype 9 (17.1%) and haplotype 1 (56.1%). This frequency of mutant haplotype 1 in Portugal is, to our knowledge, the highest for this mutant haplotype in all studies reported to date. Other mutant haplotypes were either rare (haplotype 2, 9.7%) or totally absent (haplotype 3, 0%). Only 24.5% of all mutant alleles were found to consistently carry identified mutations, particularly R261Q (9.8%), R252W (3.3%), R408W (1.6%) and delta I94 (3.3%). A new mutation, L249F, located in the seventh exon of the gene, accounted for 6.5% of all mutant alleles in our series. Interestingly, this mutant genotype was consistently associated with mutant haplotype 1 (P less than 0.01), as also observed for the R261Q mutation. It appears, therefore, that mutant haplotype 1 is genotypically heterogeneous in Portugal and that more than two mutations account for its prevalence in this country.
Alleles↗
A gene for Usher syndrome type I (USH1A) maps to chromosome 14q.
Usher syndrome (US) is an autosomal recessive disease characterized by congenital hearing impairment and retinitis pigmentosa. It is the most frequent cause of deaf-blindness in adults and accounts for 3 to 6% of deaf children. Here, we report the genetic mapping of a gene for US type I (USH1A), the most severe form of the disease, to the long arm of chromosome 14, by linkage to probe MLJ14 at the D14S13 locus in 10 families of Western France ancestry (Z = 4.13 at theta = 0). Among them, 8 families originated from a small area of the Poitou-Charentes region (Z = 3.78 at theta = 0), suggesting that a founder effect could be involved. However, since not all US type I families were found to be linked to this locus, the present study provides evidence for genetic heterogeneity of this condition (heterogeneity versus homogeneity test HOMOG, P < 0.05; heterogeneity versus no linkage, P < 0.01).
Chromosome Mapping↗
The gene for X-linked hydrocephalus maps to Xq28, distal to DXS52.
We report the study of five independent X-linked hydrocephalus (HSAS1) families with polymorphic DNA markers of the Xq28 region. A total of 58 individuals, including 7 living affected males and 22 obligate carriers, have been studied. Maximum lod score was 7.21 at theta = 2.40% for DXS52 (St14-1). A single recombination event was observed between this marker and the HSAS1 locus. Other markers studied were DXS296 (Z = 2.02 at theta = 2.5%), DXS304 (Z = 4.37 at theta = 7.8%), DXS74 (Z = 3.50 at theta = 0%), DXS15 (Z = 1.96 at theta = 5.7%), DXS134 (Z = 3.31 at theta = 0%), and F8C (Z = 5.79 at theta = 0%). These data confirm the localization of the HSAS1 gene to Xq28 and provide evidence for genetic homogeneity of this syndrome. In addition, examination of two obligate recombinant meioses along with multipoint linkage analysis supports the distal localization of the HSAS1 locus with respect to the DXS52 cluster. These observations are of potential interest for future studies aimed at HSAS1 gene characterization.
Chromosome Mapping↗
Digito-reno-cerebral syndrome: confirmation of Eronen syndrome.
In 1985, Eronen et al. described a new autosomal recessive syndrome with absence of the distal phalanges of the toes and fingers, renal defect and cerebral anomalies (dilated ventricles or seizures). Two unrelated children affected by this syndrome enable us to accept its autonomy and delineate its nosology. Variability of the expression of the renal and cerebral manifestations is emphasized.
Abnormalities, Multiple↗
The orocraniodigital syndrome of Juberg and Hayward.
We report three new isolated cases of orocraniodigital syndrome (Juberg-Hayward syndrome). The main clinical features of this unusual birth defect (six patients from three families described so far) are cleft lip/palate, hypertelorism, bowed and upward slanting eyebrows, thumb hypo/aplasia or proximal/distal thumb displacement, luxation of the radial head, elbow restriction, minor vertebral and rib anomalies, and horseshoe kidneys. New features observed in our patients are severe mental impairment (not correlated with the severity of the malformations), anterior anal displacement, and ptosis. Recessive inheritance is likely, but autosomal dominant inheritance cannot yet be totally ruled out; therefore, genetic counselling of parents of an affected child and of affected patients themselves must be cautious.
Adolescent↗
Phenotype-genotype correlations in X linked retinitis pigmentosa.
Retinitis pigmentosa (RP) represents a group of clinically heterogeneous retinal degenerations in which all modes of inheritance have been described. We have previously found two different clinical profiles in X linked RP as a function of age and mode of onset. The first clinical form has very early onset with severe myopia. The second form starts later with night blindness with mild myopia or none. At least two genes have been identified in X linked forms, namely RP2 (linked to DXS7, DXS255, and DXS14) and RP3 (linked to DXS84 and OTC) on the short arm of the X chromosome. In order to contribute to phenotype-genotype correlations in X linked RP, we tested the hypothesis that the two clinical profiles could be accounted for by the two different gene loci. The present study provides evidence for linkage of the clinical form with early myopia as the onset symptom with the RP2 gene (pairwise linkage to DXS255: Z = 3.13 at theta = 0), while the clinical form with later night blindness as the onset symptom is linked to the RP3 gene (pairwise linkage to OTC: Z = 4.16 at theta = 0).
Female↗
Confirmation and refinement of the genetic localization of the Coffin-Lowry syndrome locus in Xp22.1-p22.2.
The Coffin-Lowry syndrome (CLS) is an X-linked inherited disease of unknown pathogenesis characterized by severe mental retardation, typical facial and digital anomalies, and progressive skeletal deformations. Our previous linkage analysis, based on four pedigrees with the disease, suggested a localization for the CLS locus in Xp22.1-p22.2, with the most likely position between the marker loci DXS41 and DXS43. We have now extended the study to 16 families by using seven RFLP marker loci spanning the Xp22.1-p22.2 region. Linkage has been established with five markers from this part of the X chromosome: DXS274 (lod score [Z] (theta) = 3.53 at theta = .08), DXS43 (Z(theta) = 3.16 at theta = .08), DXS197 (Z(theta) = 3.03 at theta = .05), DXS41 (Z(theta) = 2.89 at theta = .08), and DXS207 (Z(theta) = 2.73 at theta = .13). A multipoint linkage analysis further placed, with a maximum multipoint Z of 7.30, the mutation-causing CLS within a 7-cM interval defined by the cluster of tightly linked markers (DXS207-DXS43-DXS197) on the distal side and by DXS274 on the proximal side. Thus, these further linkage data confirm and refine the map location for the gene responsible for CLS in Xp22.1-p22.2. As no linkage heterogeneity was detected, this validates the use of the Xp22.1-p22.2 markers for carrier detection and prenatal diagnosis in CLS families.
Abnormalities, Multiple↗
Spectrum of phenylketonuria mutations in western Europe and north Africa, and their relation to polymorphic DNA haplotypes at the phenylalanine hydroxylase locus.
A total of 252 chromosomes from 126 patients with phenylalanine hydroxylase (PAH) deficiencies were analyzed for both mutant genotypes and restriction fragment length polymorphism (RFLP) haplotypes at the PAH locus. The mutant genes studied originated either from Western Europe (116 alleles) or from Mediterranean countries (136 alleles). Only 27% of all mutant alleles were found to carry identified mutations, particularly mutations at codon 252 (2.3%), 261 (7.5%), 280 (6.3%), 408 (3.5%) and at the splice donor site of intron 12 (6.3%). The mutant genotypes were associated with RFLP haplotypes 7, 1, 38, 2 and 3 at the PAH locus respectively. Except for the splice mutation of intron 12, these associations were preferential, but not exclusive, since the other four mutations were found on the background of at least two RFLP haplotypes. These results, together with the observation that 85% of PAH deficient patients are heterozygotes for their mutant genotypes, emphasize the great heterogeneity of PAH deficiencies in Mediterranean countries and hamper systematic DNA testing for carrier status in this population.
Africa, Northern↗
Contribution to carrier detection and genetic counselling in X linked retinoschisis.
X linked retinoschisis (RS) is a vitreoretinal disease resulting from microcystic degeneration of the macula associated with peripheral lesions. The disease gene has already been assigned to the distal short arm of the X chromosome (Xp22.2) by linkage studies. In order to contribute both to a better localisation of the RS locus and to genetic counselling in RS families, we have carried out a clinical and genetic analysis in seven pedigrees. We show, first, that in contrast with previous reports, heterozygote carriers frequently express the disease, and display peripheral retinal alterations similar to those found in affected males. Second, while distal markers DXS16, DXS207, and DXS43 are closely linked to the disease locus, a high level of recombination events was found with centromeric markers, namely DXS274, DXS41, and DXS164. These findings must be taken into account for both carrier detection and prenatal diagnosis in X linked RS.
Female↗
Lethal progeroid syndrome with osteolysis. Case report.
A particular progeroid syndrome with severe acro-osteolysis, cutaneous changes, failure to thrive, and early death is described in a young boy. Progeria and mandibulo-acral dysplasia are discussed, but early death is unusual in these two syndromes. This observation raises the question of a large spectrum including all of these syndromes.
Humans↗