306 DIABETES, VOL. 49, FEBRUARY 2000 Brief Genetics Report Genetic Variation in the Hepatocyte Nuclear Factor-3 Gene ( H N F3B) Does Not Contribute to Maturity-Onset Diabetes of the Young in French Cau casian s Amar Abderrahmani, Jean-Claude Chèvre, Shuichi Otabe, Mohamed Chikri, El Habib Hani, Martine Vaxillaire, Yoshinori Hinokio, Yukio Horikawa, Graeme I. Bell, and Philippe Froguel Mutations in genes encoding hepatocyte nuclear factor (HNF) are responsible for three of the five subtypes of maturity-onset diabetes of the young (MODY). This observation and molecular studies indicate that the HNF network is required for normal function of pan- creatic -cells. This suggests that transcription factors involved in this complex network are candidates for genetic defects in MODY. Because the HNF-3 gene is implicated in this network, we screened it for muta- tions in 21 probands of French ancestry with clinical diagnosis of MODY and early-onset type 2 diabetes. All of the five known MODY genes, HNF-4 , glucokinas e, HN F-1 , HN F-1 , and IPF1, were previously excluded as being the cause of diabetes in these families. By direct sequencing, we identified two transitions, an A-to-G at position –213 and a C-to-T at position –63 in the pro- moter and exon 1, respectively, of the HNF-3 gene. A G-to-C transversion at position +32 in the intron 1 and three transitions, C-to-T at position 291, A-to-G at posi- tion 837, and G-to-A at position 1188 in the exon 3, resulting in noncoding mutations Ala97Ala, Gly279Gly, and Gln396Gln, respectively, were also identified. The allele frequencies were not significantly diff e re nt between a control group and MODY probands. Familial segregation studies and linkage analysis showed that genetic variation in the HNF-3 gene is unlikely to be the cause of early-onset type 2 diabetes in these Cau- casian families. Diabetes 4 9 :3 0 6–308, 2000 M aturity-onset diabetes of the young (MODY) is a group of metabolic disorders characterized by early-onset diabetes, autoso mal dominant inheritance, and a primary defect in glucose- stimulated insulin secretion (1). The hepatocyte nuclear fac- tors (HNFs) are a structurally diverse group of transcription factors that were originally identified in the context of liver- specific regulation of gene expression (2). Mutations in genes encoding three members of this group, HN F-4 , HN F-1 , and HN F-1 , have been shown to be the causes of three of the five forms of MODY, MODY1, MODY3, and MODY5 (3–5). HNF-4 is an upstream regulator of HN F-1 gene expression (6), and HNF-1 and HNF-1 can activate gene expression as homodimers as well as heterodimers and together comprise a transcriptionally active complex (7). The genetic and molecular biological studies of HNF func- tio n indicate that an intac t HNF netwo rk is required fo r no r- mal function of pancreatic -cells and consequently for nor- mal regulation of glucose metabolism. Thus, it was sug- gested that transcription factors involved in this complex network are candidates for genetic defects in diabetes (8). The HN F-3 gene ( HN F3B) located on human chromosome 20p11 encodes a member of HNF-3/Forkhead winged helix family and is expressed in pancreatic - and -cells (9). H NF-3 regulates the expression of the insulin promoter fac to r-1 gene ( IPF1), mutations of which are the cause of a fourth described form of MODY, MODY4 (10,11). It is also a positive regulator of expression of the HN F-4 and HN F-1 genes and their downstream targets (8). Finally, a mutation in an HNF-3–responsive element in the promoter of the HN F-1 gene has recently been identified in a MODY patient (11a). All of these data suggest that HN F3B is a plausible can- didate for heritable defects in MODY. This prompted us to screen the coding region, 23 nucleotides of the promoter, and the untranslated exon 1 of the HN F3B gene for mutations in 21 MODY probands of French ancestry. The probands’ clinical characteristics are described in Table 1. Of these, 11 were selected from families with a clinical diagnosis of MODY (12). The other 10 were from MODY-like families. All of the five known MODY genes From the Unité Propre de Recherche de l’Enseignement Supérieur Asso ciée au Centre National de la Recherche Scientifique (CNRS UPRES-A) 8090 (A.A., J.-C.C., S.O., M.C., E.H.H., M.V., P.F.), Institut de Biologie de Lille, Lille, France; and the Howard Hughes Medical Institute and the Departments of Biochemistry and Molecular Biology, Medicine, and Human Genetics ( Y.Hi., Y.Ho., G.I.B.), University of Chicago, Chicago, Illinois. Address correspondence and reprint requests to Dr. P. Froguel, CNRS UPRES-A 8090, Institut de Biolo gie de Lille, 1 rue du Professeur Calmette, BP 245, 59019 Lille Cedex, France. E-mail: froguel@ pasteur-lille .f r. Received for publication 3 June 1999 and accepted in revised form 25 October 1999. A.A. and J.-C.C. contributed equally to this work. HNF, hepatocyte nuclear factor; IPF-1, insulin promoter factor-1; LOD, logarithm of odds; MODY, maturity-onset diabetes of the young; PCR, poly- merase chain reaction.