Congenital afibrinogenemia (Mendelian Inheritance in Man #202400) is a rare, autosomal recessive disorder characterized by the complete absence of circulating fibrinogen. Our recent studies on the molecular basis of the disease showed that the most common genetic defect is a donor splice mutation in fibrinogen alpha gene (FGA) intron 4, IVS4؉1G>T. Two other FGA donor splice mutations, in intron 1 (IVS1؉3A>G) and intron 3 (IVS3؉1_؉4delGTAA), were identified in afibrinogenemia patients. Because it was impossible to directly study the effect of these mutations on mRNA splicing in patient hepatocytes, we used a transfected cell approach, which previously allowed us to show that the common IVS4 mutation causes afibrinogenemia due to the activation of multiple cryptic donor splice sites. In this study, analysis of the IVS3delGTAA mutation showed exon 3 skipping in 99% of transcripts and exons 2 and 3 skipping in 1% of transcripts. The different outcomes of these donor splice mutations appear to follow the model proposed in a study of fibrillar collagen genes, where donor splice mutations occurring in a rapidly spliced intron with respect to upstream introns lead in most cases to exon skipping, while mutations in later-spliced introns lead to intron inclusion or cryptic splice-site utilization. Indeed, we found that in FGA intron 3 was preferentially spliced first, followed by intron 2, intron 4, and intron 1. (Blood. 2003;

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Congenital afibrinogenemia, the most severe form of fibrinogen deficiency, is characterized by the complete absence of fibrinogen. The disease is caused by mutations in 1 of the 3 fibrinogen genes FGG, FGA, and FGB, clustered on the long arm of human chromosome 4. The majority of cases are due to null mutations in the FGA gene although one would expect the 3 genes to be equally implicated. However, most patients studied so far are white, and therefore the identification of causative mutations in non-European families is necessary to establish if this finding holds true in all ethnic groups. In this study, we report the identification of a novel nonsense mutation (Arg134Xaa) in the FGG gene responsible for congenital afibrinogenemia in 10 patients from Lebanon. Expression studies in COS-7 cells demonstrated that the Arg134Xaa codon, which is encoded by adjacent exons (TG-intron 4-A) affected neither mRNA splicing nor stability, but led to the production of an unstable, severely truncated fibrinogen ␥ chain that is not incorporated into a functional fibrinogen hexamer. ( IntroductionInherited disorders of fibrinogen are rare and affect either the quantity (hypofibrinogenemia and afibrinogenemia) or the quality (dysfibrinogenemia) of circulating fibrinogen. Fibrinogen is produced in the liver from 3 homologous polypeptide chains, A␣, B␤, and ␥, which assemble to form a hexamer containing 2 copies of each chain. Fibrinogen is the precursor of fibrin, the major protein constituent of the blood clot. Congenital afibrinogenemia (OMIM: online Mendelian Inheritance in Man; no. 202400), 1 the most severe form of fibrinogen deficiency, is characterized by the complete absence of fibrinogen. The disease was originally described in 1920; 2 it has an estimated prevalence of around 1 to 2 in 1 000 000. Umbilical cord hemorrhage is often the first sign of the disorder; gum bleeding, epistaxis, menorrhagia, gastrointestinal bleeding, and hemarthrosis occur with varying intensity, and spontaneous intracerebral bleeding and splenic rupture can occur throughout life. 3,4 Congenital afibrinogenemia is inherited in an autosomal recessive manner: the condition exists only when both alleles are mutated, in homozygosity or compound heterozygosity; both sexes are affected. Although the disease was first described in 1920, the genetic locus responsible for the disorder was only recently determined. We identified the first causative mutations for this disorder in a nonconsanguineous Swiss family. The genetic defect was an apparently recurrent deletion of approximately 11 kb of DNA that eliminates the majority of the FGA gene and so leads to a complete absence of functional fibrinogen. 5 The deletions were all identical to the base pair and probably resulted from nonhomologous (illegitimate) recombination, mediated by a direct 7 bp repeat, AACTTTT, and perhaps also by indirect repeats in the breakpoint region. Many families with this disorder have been studied since then, allowing the identification of numerous causative mutations (reviewe...

Contagious bovine pleuropneumonia is a serious threat to cattle not only in Africa but also in southern Europe and possibly Asia. It is now present in countries that had been free of the disease for many years, giving rise to doubts about the efficiency of the control strategies. In Africa CBPP is controlled mainly by a vaccination policy that uses variant strains of Mycoplasma mycoides subsp mycoides biotype SC, called T1/44 or T1sr. Until recently, it was not possible to differentiate the various strains within the biotype and consequently to identify the vaccine strains. Restriction analysis of mycoplasma DNA with HindIII and Pst1 has been applied to 24 strains of African origin and one European strain. Each enzyme gave rise to different restriction profiles and the combination of the results permitted subdivision of these strains into 9 groups. Interestingly, some profiles of pathogenic strains seem to be restricted to certain geographical areas. The profile of the poorly immunogenic vaccinal strain KH3J is also very peculiar, and it is easily distinguished from that of the other vaccine strains originating from T1. This technique is simple once the strains are isolated. Efforts are now under way to use molecular tools based on PCR products to alleviate the difficulty of isolation.