Axonemal beta heavy chain dynein DNAH9: cDNA sequence, genomic structure, and investigation of its role in primary ciliary dyskinesia

Dyneins are multisubunit protein complexes that couple ATPase activity with conformational changes. They are involved in the cytoplasmatic movement of organelles (cytoplasmic dyneins) and the bending of cilia and flagella (ax onemal dyneins), Here we present the first complete cDNA and genomic sequen ces of a human axonemal dynein beta heavy chain gene, DNAH9, which maps to 17p12. The 14-kb-long cDNA is divided into 69 exons spread over 390 kb. The cDNA sequence of DNAH9 was determined using a combination of methods inclu ding 5' rapid amplification of cDNA ends, RT-PCR, and cDNA library screenin g. RT-PCR using nasal epithelium and testis RNA revealed several alternativ ely spliced transcripts. The genomic structure was determined using three o verlapping BACs sequenced by the Whitehead Institute/MIT Center for Genome Research. The predicted protein, of 4486 amino acids, is highly homologous to sea urchin axonemal beta heavy chain dyneins (67% identity). It consists of an N-terminal stem and a globular C-terminus containing the four P-loop s that constitute the motor domain. Lack of proper ciliary and flagellar mo vement characterizes primary ciliary dyskinesia (PCD), a genetically hetero geneous autosomal recessive disorder with respiratory tract infections, bro nchiectasis, male subfertility, and, in 50% of cases, situs inversus (Karta gener syndrome, KS). Dyneins are excellent candidate genes for PCD and KS b ecause in over 50% of cases the ultrastructural defects of cilia are relate d to the dynein complex. Genotype analysis was performed in 31 PCD families with two or more affected siblings using a highly informative dinucleotide polymorphism located in intron 26 of DNAH9, Two families with concordant i nheritance of DNAH9 alleles in affected individuals were observed. A mutati on search was performed in these two "candidate families," but only polymor phic variants were found. In the absence of pathogenic mutations, the DNAH9 gene has been excluded as being responsible for autosomal recessive PCD in these families, (C) 2001 Academic Press.