IDENTIFICATION OF 7 RAT AXONEMAL DYNEIN HEAVY-CHAIN GENES - EXPRESSION DURING CILIATED CELL-DIFFERENTIATION

Axonemal dyneins are molecular motors that drive the beating of cilia and flagella. We report here the identification and partial cloning of seven unique axonemal dynein heavy chains from rat tracheal epithelia l (RTE) cells. Combinations of axonemal-specific and degenerate primer s to conserved regions around the catalytic site of dynein heavy chain s were used to obtain cDNA fragments of rat dynein heavy chains. South ern analysis indicates that these are single copy genes, with one poss ible exception, and Northern analysis of RNA from RTE cells shows a tr anscript of similar to 15 kb for each gene. Expression of these genes was restricted to tissues containing axonemes (trachea, testis, and br ain). A time course analysis during ciliated cell differentiation of R TE cells in culture demonstrated that the expression of axonemal dynei n heavy chains correlated with the development of ciliated cells, whil e cytoplasmic dynein heavy chain expression remained constant. In addi tion, factors that regulate the development of ciliated cells in cultu re regulated the expression of axonemal dynein heavy chains in a paral lel fashion. These are the first mammalian dynein heavy chain genes sh own to be expressed specifically in axonemal tissues. Identification o f the mechanisms that regulate the cell-specific expression of these a xonemal dynein heavy chains will further our understanding of the proc ess of ciliated cell differentiation.