COMPLEMENTARY DEOXYRIBONUCLEIC-ACID CLONING AND CHARACTERIZATION OF APUTATIVE HUMAN AXONEMAL DYNEIN LIGHT-CHAIN GENE

Immotile Cilia Syndrome (ICS) is characterized by recurrent sinus and lung infections, bronchiectasis, and sperm immotility. Nasal cilia and sperm tails in patients with ICS exhibit a variety of ultrastructural defects, often including shortening or absence of the inner dynein ar ms. Immotile mutant strains of Chlamydomonas, a biflagellated algae, h ave ultrastructural defects similar to those seen in patients with thi s clinical disorder. Furthermore, splice-site mutations in the Chlamyd omonas inner dynein arm gene (p28) are associated with impaired flagel lar motility. We therefore hypothesized that the human homologue of th e Clamydomonas dynein p28 gene would be an attractive candidate gene f or patients with ICS. Accordingly, we cloned the full length complemen tary DNA (cDNA) and genomic clone by screening of appropriate librarie s and databases, using the protein sequence of the Chlamydomonas p28 g ene. The human homologue is encoded by a 921 bp transcript (accession no. AF006386) with an open reading frame of 257 amino acids. Using som atic cell and radiation hybrid panels, the hp28 gene was mapped to hum an chromosome 1p35.1. The hp28 cDNA probe hybridizes to sequences in a ll species on a zoo blot containing genomic DNA from yeast to human. N orthern blot analysis reveals two hp28 gene transcripts, 0.9 and 2.5 k b, in many tissues. The 0.9 kb transcript is expressed at a 20-fold hi gher level than the 2.5-kb transcript in the testis. The entire gene i s included in a 20-kb EcoRI genomic fragment and has 7 exons and 6 int rons. Cloning of the hp28 cDNA and mapping of the intron-exon junction s should now make it possible to test whether a subset of ICS is a con sequence of mutations in the human axonemal dynein light chain gene hp 28.