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J Frézal

Publications and source records attributed to J Frézal.

At least 19 recordsLinked to original sources
PubMed2000

The photoreceptor cell-specific nuclear receptor gene (PNR) accounts for retinitis pigmentosa in the Crypto-Jews from Portugal (Marranos), survivors from the Spanish Inquisition.

The last Crypto-Jews (Marranos) are the survivors of Spanish Jews who were persecuted in the late fifteenth century, escaped to Portugal and were forced to convert to save their lives. Isolated groups still exist in mountainous areas such as Belmonte in the Beira-Baixa province of Portugal. We report here the genetic study of a highly consanguineous endogamic population of Crypto-Jews of Belmonte affected with autosomal recessive retinitis pigmentosa (RP). A genome-wide search for homozygosity allowed us to localize the disease gene to chromosome 15q22-q24 (Zmax=2.95 at theta=0 at the D15S131 locus). Interestingly, the photoreceptor cell-specific nuclear receptor (PNR) gene, the expression of which is restricted to the outer nuclear layer of retinal photoreceptor cells, was found to map to the YAC contig encompassing the disease locus. A search for mutations allowed us to ascribe the RP of Crypto-Jews of Belmonte to a homozygous missense mutation in the PNR gene. Preliminary haplotype studies support the view that this mutation is relatively ancient but probably occurred after the population settled in Belmonte.

Chromosomes, Human, Pair 15↗
PubMed1998

Genatlas database, genes and development defects.

This article aims to illustrate the potentialities of the Genatlas database, taking, as an example, the developmental genes and their associated diseases in man. These genes belong to several categories intervening from the first stages of embryonic life. They operate at all steps of developmental cascades from extracellular signaling to activation of target genes. Quite a number of those genes have been identified in man, which are the orthologs of genes previously described in lower species. These genes are mapped and an increasing number are associated with developmental anomalies. These studies shed light on the mechanisms of congenital malformations. They disclose a large array of genetic and phenotypic heterogeneity and a high degree of complexity.

Body Patterning↗
PubMed1998

The role of the SMN gene in proximal spinal muscular atrophy.

Childhood spinal muscular atrophy (SMA) is a common recessive autosomal disorder that results in degeneration of lower motor neurons. The identification of the disease gene, Survival of Motor Neuron (SMN), was a major advance in understanding the molecular basis underlying this devastating neuromuscular disease. This finding has greatly improved the genetic counselling of SMA families. Recently, biochemical studies demonstrated its involvement in the biogenesis of spliceosomal snRNPs, suggesting a critical role of SMN in RNA processing. Surprisingly, other studies showed a putative role of SMN in an anti-apoptotic pathway involving Bcl-2. The function of SMN protein is not fully understood. These observations emphasized the difficulty in elucidating the function of any novel protein. Therefore, multidisciplinary approaches are required to understand the pathogenesis of SMA.

Animals↗
PubMed1996

Retinal-specific guanylate cyclase gene mutations in Leber's congenital amaurosis.

Leber's congenital amaurosis (LCA, MIM 204,000), the earliest and most severe form of inherited retinopathy, accounts for at least 5% of all inherited retinal dystrophies. This autosomal recessive condition is usually recognized at birth or during the first months of life in an infant with total blindness or greatly impaired vision, normal fundus and extinguished electroretinogram (ERG). Nystagmus (pendular type) and characteristic eye poking are frequently observed in the first months of life (digito-ocular sign of Franceschetti). Hypermetropia and keratoconus frequently develop in the course of the disease. The observation by Waardenburg of normal children born to affected parents supports the genetic heterogeneity of LCA. Until now, however, little was known about the pathophysiology of the disease, but LCA is usually regarded as the consequence of either impaired development of photoreceptors or extremely early degeneration of cells that have developed normally. We have recently mapped a gene for LCA to chromosome 17p13.1 (LCA1) by homozygosity mapping in consanguineous families of North African origin and provided evidence of genetic heterogeneity in our sample, as LCA1 accounted for 8/15 LCA families in our series. Here, we report two missense mutations (F589S) and two frameshift mutations (nt 460 del C, nt 693 del C) of the retinal guanylate cyclase (RETGC, GDB symbol GUC2D) gene in four unrelated LCA1 probands of North African ancestry and ascribe LCA1 to an impaired production of cGMP in the retina, with permanent closure of cGMP-gated cation channels.

Blindness↗
PubMed1995

[Fifty years of medical genetics. A tribute to Maurice Lamy on the hundredth anniversary of his birth].

Before 1960, no disease gene had been mapped to human chromosome apart from the sex-linked characters which are carried by the X chromosome. The first assignments were inferred from the results of somatic cells hydridization and concerned enzymatic deficiencies and protein defects. They were followed by the data gained from the cytogenetics studies of microrearrangements, either deletions or translocations. The family and linkage studies began to be successfully undertaken following the discovery of polymorphic probes. The breakthrough came out with the availability of highly polymorphic microsatellites scanning quite evenly, the major part of the genome. Currently, more than 1,000 clinical disorders are mapped and compiled in the database GID/GENATLAS. They concern all chapters and extend to characters which are usually sporadic, such as malignant tumours and congenital malformations. The mapping endeavour already had great impact on our understanding of fundamental life processes and unveiled the extent of genetic heterogeneity of diseases. Its major consequences concern prenatal diagnosis. The applications tend to extend towards presymptomatic diagnosis, and screening of carriers, two procedures still controversial, which request due consideration of their inherent risks and side effects and cannot be undertaken without the informed consent of patients. Predictive testing for the detection of liabilities is still a subject of lively debate. Although the spectacular advances of mapping and its implications open great hopes for the prevention and even cure of disease, care has to be taken to their limits and risks and, in their approach, full consideration must be given the respect if human person.

France↗
PubMed1993

[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↗
PubMed1992

[Phenylketonuria yesterday and today. Evaluation of the work of systematic neonatal screening].

Phenylketonuria is due in the very great majority of cases to a deficiency in phenylalanine hydroxylase, an enzyme whose cofactor is biopterin. Prenatal screening consists in measuring the concentration of phenylalanine in a sample of dried blood taken after birth (levels are already raised by day 3). Screening, organized by the Association française pour le dépistage et la prévention des handicaps de l'enfant, is very thorough (cover greater than 99%). Treatment involves observance of dietary restriction for at least five years. Results are good. Questions concerning the useful duration of dietary treatment, the level of phenylalanine that should not be exceeded, and the future of girls with PKU remain controversial. When adult, such girls may give birth to retarded children if they do not resume dietary restriction before becoming pregnant. Now that problems of screening, its organization, and the management of diet have been solved, these questions are the new challenge that faces us.

Female↗
PubMed1992

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↗
PubMed1992

Mapping the eye diseases.

In this review the authors first give an overview of the general strategies of mapping which differ whether the biochemical (molecular) defect of the disease is known or not. The main problems besides mapping are concerned for the first category with the correlation between mutation and phenotype and for the second, with heterogeneity, genetic vs phenotypic. Finally, tables are displayed of eye diseases or diseases with eye involvement (metabolic or not) which have been currently mapped, as well as candidate genes actually or putatively involved in visual transduction.

Chromosome Mapping↗
PubMed1991

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↗
PubMed1991

In situ hybridization of two markers closely flanking the spinal muscular atrophy gene to 5q12----q13.3.

In order to refine the physical location of the p105-153Ra and M4 probes which closely flank the spinal muscular atrophy gene (SMA) on human chromosome 5q, in situ hybridization has been carried out on prometaphase chromosomes. Our results demonstrate that the disease gene is located between the 5q12----q13.1 and 5q13.3 bands. The present study will hopefully contribute to microdissection of the chromosomal region of the SMA gene.

Child↗
PubMed1991

Linkage analysis in spinal muscular atrophy, by six closely flanking markers on chromosome 5.

The proximal spinal muscular atrophies (SMA) represent the second most common autosomal recessive disorder, after cystic fibrosis. The gene responsible for chronic SMA has recently been mapped to chromosome 5q by using genetic linkage studies. Among six markers mapping to this region, five were shown to be linked with the SMA locus in 39 chronic SMA families each containing at least two affected individuals. Multilocus analysis by the method of location score was used to establish the best estimate of the SMA gene location. Our data suggest that the most likely location for SMA is between loci D5S6 and D5S39. The genetic distances between these two markers are estimated to be 6.4 cM in males and 11.9 cM in females. Since meiosis were informative with D5S39 and D5S6 in 92% and 87% of SMA families, respectively, it is hoped that the present study will contribute to the calculation of genetic risk in SMA families.

Chromosome Mapping↗