Segregation analysis of Alagille syndrome.

Alagille syndrome (AGS) is a well defined genetic disorder characterised by five major features. An autosomal dominant mode of transmission with reduced penetrance has been suggested by the analysis of a limited number of families. However there has been no statistical analysis. We report here the first segregation analysis of AGS, using 33 families collected through 43 probands. Segregation analysis of these families allowed us to conclude that AGS is transmitted as a dominant disorder with 94% penetrance and 15% of cases are sporadic. The expressivity of the phenotype was variable and 26 persons (15 parents and 11 sibs) were identified as presenting minor forms of the disease. These results are valuable for genetic counselling

The olig family: phylogenetic analysis and early gene expression in Xenopus tropicalis.

International audienceThe olig genes form a small subfamily of basic helix-loop-helix transcription factors. They were discovered in 2000 as genes required for oligodendrocyte lineage specification. Since then, olig genes have been identified in various vertebrate species and corresponding sequences accumulated within genomic databases. Until now, three groups of olig genes have been characterized. Our phylogenetic analysis demonstrates the existence of a fourth group, which we named olig4. Genes of the four olig groups are present in actinopterygians and amphibians, whereas mammals only possess olig1, 2, and 3. We also found one olig gene in hemichordates, urochordates, and cephalochordates. Our expression study during Xenopus tropicalis embryogenesis shows that the four olig genes have very distinct expression patterns. Olig1 is very faintly expressed before the tadpole stage, whereas olig2, 3, and 4 are expressed from the gastrula stage onward. The olig3 expression during neurulation suggests a role in early anteroposterior patterning of the brain. All these results indicate that olig genes are involved in several developmental processes during early development

Deleted Chromosome 20 from a patient with Alagille syndrome isolated in a cell hybrid through leucine transport selection: study of three candidate genes

International audienceAlagille syndrome (AGS) is a well-defined ge-netic entity assigned to the short arm of Chromosome(Chr) 20 by a series of observations of AGS patients as-sociated with microdeletions in this region. By fusing lym-phoblastoid ceils of an AGS patient that exhibited a mi-crodeletion in the short arm of Chr 20 encompassing bandspl 1.23 to p12.3 with rodent thermosensitive mutant cells(CHOtsH 1-1) deficient in-leucyl-tRNA synthetase, we iso-lated a somatic cell hybrid segregating the deleted humanChr 20. This hybrid clone, designated NR2, was charac-terized by several methods, including PCR, with eightpairs of oligonucleotides mapped to Chr 20: D20S5,D20S41, D20S42, D20S56, D20S57, D20S58, adenosinedeaminase (ADA), and Prion protein (PRIP); RestrictionFragment Length Polymorphism (RFLP) analyses withfour genomic anonymous probes (D20S5, cD3H12,D20S 17, D20S 18); and fluorescent in situ hybridization(FISH) with total human DNA and D20Z1, a sequencespecific to the human Chr 20 centromere, as probes.The NR2 hybrid allowed us to exclude three candidategenes for AGS: hepatic nuclear factor 3 [3 (HNF3[3), pairedbox 1 (PAX1), and cystatin C (CST3) as shown by theirlocalization outside of the deletion. The NR2 hybrid is apowerful tool for the mapping of new probes of this region,as well as for obtaining new informative probes specific forthe deletion by subtractive cloning of the region. Suchmarkers will be useful for linkage analysis and screeningof cDNA libraries

Effet du polymorphisme (AA/GC) au locus DGAT1 sur l'activité transcriptionnelle du tissu mammaire bovin, sur la composition du lait et sur les caractéristiques des globules gras et des micelles de caséines

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ALAGILLE SYNDROME - FAMILY STUDIES

Alagille syndrome (AGS) is one of the major forms of chronic liver disease in childhood with severe morbidity and a mortality of 10 to 20%. It is characterised by cholestasis of variable severity with paucity of interlobular bile ducts and anomalies of the cardiovascular system, skeleton, eyes, and face. Previous studies suggest a wide variation in the expression of the disease and a high incidence of new mutations. To determine more accurately the rate of new mutations and to develop criteria for detecting the disorder in parents we systematically investigated parents in 14 families with an affected child. Clinical examination was supplemented by liver function tests, echocardiography, radiographic examination of the spine and forearm, ophthalmological assessment, and chromosome analysis. Six parents had typical anomalies in two or more systems pointing to the presence of autosomal dominant inheritance. Systematic screening of parents for the features defined in this study should improve the accuracy of genetic counselling