SHORT COMMUNICATION Sequence Characterization of a Newly Identified Human a-Tubulin Gene (TUBA2) Catherine Dode ´, 1 Dominique Weil, Jacqueline Levilliers, Fabien Crozet, Hassan Chaı¨b, Fabienne Levi-Acobas, Parry Guilford, and Christine Petit Unite ´ de Ge ´ne ´tique des De ´ficits Sensoriels, CNRS URA 1968, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France Received November 12, 1996; accepted October 21, 1997 two different genes, Ma3 and Ma7 (23). Due to the We report on the isolation and initial characteriza- very high rate of sequence identity among the different tion of a human a-tubulin gene named TUBA2. This cDNAs corresponding to the same isoform, the isolation gene is located in the 13q11 region and has been consid- of an a-tubulin cDNA is a difficult task unless a single ered a candidate gene for two nonsyndromic deaf- recombinant phage (or plasmid) contains the full- nesses, DFNB1 and DFNA3. The gene, with a minimum length cDNA. Finally, in addition to the genetic com- size of 6.5 kb, contains five exons and four introns start- plexity, diversity may also be generated at the protein ing at codon positions 1, 76, 125, and 352, one of which level by posttranslational modifications including de- is inserted between the initiation methionine codon tyrosination/tyrosination (2), acetylation (17), and glu- and the codon specifying the second amino acid, argi- tamylation (5). nine 2. Neither rearrangement nor point mutation was Which isoforms of a-tubulin are present in the co- found in the coding region of the gene in DFNB1- and chlea (inner ear) is presently unknown. In the sup- DFNA3-affected patients. The gene was therefore un- porting cells of the cochlear neuroepithelium, micro- likely to be responsible for either of these deafnesses. tubules contain 15 rather than 13 protofilaments During the characterization of TUBA2, the gene encod- (19) and are interdigitated with and cross-linked to ing connexin 26 was proven to be responsible for both actin filaments (21). In these cells, the microtubules DFNB1 and DFNA3 (D. P. Kelsell et al., 1997, Nature 387: 80–83). However, the present data offer the possi- are stable and contain high amounts of detyrosi- bility of testing the involvement of the TUBA2 gene in nated, acetylated, and polyglutamylated a-tubulin the Clouston hidrotic ectodermal dysplasia and the Ka- (22). In the sensory hair cells, it has been shown that buki syndrome, two genetic diseases that have recently microtubules form networks that run throughout the been mapped to the 13q11 region.  1998 Academic Press cells and form a dense mat just below the cuticular plate (20). In mature hair cells a-tubulin is mainly tyrosinated, which is a characteristic of microtu- a- and b-tubulins are the major protein components bules undergoing rapid cycles of polymerization–de- of microtubules, which are ubiquitous cellular struc- polymerization. Finally, a-tubulin is also a compo- tures found in eukaryotic organisms. They are respon- nent of the kinocilium, a transient structure of the sible for a variety of functions, including cell division, embryonic cochlear hair cells that is involved in the cell polarity, structural support, and intracellular growth of stereocilia. transport (18). a-Tubulins consist of various isoforms In our attempt to isolate the gene(s) involved in two that are encoded by a multigene family. In mammals, forms of human nonsyndromic deafness mapping in there are at least five a-tubulin isoforms expressed in the 13q11 region, DFNA3 and DFNB1 (3, 7), we have specific cell types or at specific stages of development constructed a YAC contig of this region (8). Alu-PCR (23). Most of the isoform-specific amino acid residues fragments from the largest YAC (987e10) of the candi- are clustered in the carboxy terminus region involved date region were used to screen a mouse cochlear cDNA in interactions with microtubule-associated proteins. library, and an a-tubulin cDNA fragment was thereby In addition, a given a-tubulin isoform can be encoded isolated (8). In the present study, this YAC was sub- by different genes: for instance, one mouse a-tubulin cloned in lGEM11, and a single recombinant phage expressed exclusively in the testis is encoded by at least was isolated using the mouse cDNA fragment as a probe. Southern blot analysis of this phage revealed the same three EcoRI fragments as observed with YAC Sequence data from this article have been deposited with the Gen- 987e10 (8). Sequence comparison between part of the Bank Data Library under Accession No. AF005392. 6-kb EcoRI fragment and an EST named TUBA2 (Gen- 1 To whom correspondence should be addressed. Telephone: (33) 1 45 68 88 89. Fax: (33) 1 45 67 69 78. Bank Accession No. L11645) encoding the 98 C-termi- 125 GENOMICS 47, 125–130 (1998) ARTICLE NO. GE975081 0888-7543/98 $25.00 Copyright  1998 by Academic Press All rights of reproduction in any form reserved. AID GENO 5081 / 6r56$$$$$1 12-10-97 22:54:56 gnmxas