Complete genomic sequence of the 471 kb Familial Dysautonomia candidate region on chromosome 9q31. M. Leyne¹, J. Mull¹, S.P. Gill¹, C.B. Liebert¹, C.M. Robbins², H.W. Pinkett², I. Makalowska², C. Maayan³, A. Blumenfeld³, F.B. Axelrod⁴, M. Brownstein², B.P. Chadwick¹, J.F. Gusella¹, S.A. Slaugenhaupt¹. 1) Harvard Inst. of Human Genetics, Mass. General Hospital, Boston, MA; 2) National Institute of Health, Bethesda, MD; 3) Hadassah University Hospital, Jerusalem, Israel; 4) New York University Medical Center, New York, NY.

   Familial Dysautonomia (FD) is an autosomal recessive disorder that affects the development and survival of sensory, sympathetic and some parasympathetic neurons. The gene defect is almost exclusively limited to the Ashkenazi Jewish population where the carrier frequency is 1:30. The FD gene maps to human chromosome 9q31 and recent haplotype analysis of 441 disease chromosomes has refined the candidate interval to a 471 kb region. A detailed physical map spanning this interval was constructed and consists of 3 overlapping BAC clones and 58 cosmids. We have used exon trapping and cDNA selection to identify 8 candidate genes in the FD region. In order to refine the candidate interval and isolate new FD candidate genes, we determined the genomic sequence of the 471 kb critical region by direct sequencing of the BAC clones. The genomic sequence has yielded several new polymorphisms that have narrowed the candidate region from 471 kb to 162 kb. In addition, gene prediction programs identified three new FD candidate genes. In total, 8 of the 11 candidate genes isolated to date map within the new 162 kb critical region.The genomic structure of these genes has been determined and mutational analysis of the coding sequence of these candidate genes was performed by sequencing RT-PCR products from affected and control individuals. No pathogenic mutations were identified within the coding regions of any of our candidate genes suggesting that the FD mutation may be located in an intron or in an untranslated region of one of these genes. A cosmid library from an FD patient homozygous for the FD haplotype has been constructed and we are currently constructing an FD contig of our candidate region. Direct sequence analysis of the FD contig sequence compared with the control contig sequence will allow us to identify the mutation resulting in FD.