PF20 gene product contains WD repeats and localizes to the intermicrotubule bridges in Chlamydomonas flagella.

Abstract

The central pair of microtubules and their associated structures play a significant role in regulating flagellar motility. To begin a molecular analysis of these components, we generated central apparatus-defective mutants in Chlamydomonas reinhardtii using insertional mutagenesis. One paralyzed mutant recovered in our screen contains an allele of a previously identified mutation, pf2O. Mutant

Haploinsufficiency for the murine orthologue of Chlamydomonas PF20 disrupts spermatogenesis

“…The present study explored the function of the murine orthologue of the Chlamydomonas PF20 gene, which when mutated causes flagellar paralysis and loss of the central pair of microtubules in isolated axonemes. The Chlamydomonas PF20 gene encodes a 67-kDa protein localized in the bridges connecting the two central microtubules (12). The mouse Pf20 gene encodes two major transcripts, regulated by two different promoters (Z.Z.…”

“…The phenotype of the PF20 mutation in Chlamydomonas, where the flagella are paralyzed and the central apparatus is missing from isolated axonemes (12), predicted an abnormality in axonemal structure in mutant mice. Indeed, the ultrastructural disorganization seen in transverse sections of flagella of epididymal sperm from the chimeric mice could be viewed as being consistent with a key role for PF20 in stability of the axoneme.…”

“…However, studies of Chlamydomonas rheinhardtii revealed important roles for the central apparatus. Mutant Chlamydomonas strains lacking functional PF16, PF6, and PF20 have paralyzed flagella, and the C1 microtubule, the projections connecting the C1 microtubule and the entire central pair, respectively, are missing in isolated axonemes (11)(12)(13).To understand the function of the central apparatus in mammals, we cloned the human and mouse orthologues of Chlamydomonas, PF16 (SPAG6) (14, 15) and PF20 (16). SPAG6-deficient mice are hydrocephalic, and males surviving to maturity are infertile as a result of a marked sperm motility defect associated with disorganization of flagellar structures, including loss of the central pair microtubules and disorganization of the outer dense fibers and fibrous sheath (6).…”

“…However, studies of Chlamydomonas rheinhardtii revealed important roles for the central apparatus. Mutant Chlamydomonas strains lacking functional PF16, PF6, and PF20 have paralyzed flagella, and the C1 microtubule, the projections connecting the C1 microtubule and the entire central pair, respectively, are missing in isolated axonemes (11)(12)(13).…”

The radial spokes and central apparatus: Mechano‐chemical transducers that regulate flagellar motility

“…Chemical signaling also includes axonemal enzymes that are not directly sensitive to second messengers including casein kinase 1 (CK1), PP1, and PP2A, all of which appear to be involved in the control of dynein-driven motility [Walczak and Nelson, 1993; Central apparatus-associated polypeptides PF6 238-kDa alanine/proline rich protein; pf6 flagella lack the 1a projection on the C1 microtubule and display only twitching motion [Dutcher et al, 1984;Rupp et al, 2001] PF16 57-kDa armadillo repeat containing protein that localizes to the c1 microtubule; pf16 flagella lack the C1 microtubule and are paralyzed. PF16 may correspond to CP14 [Dutcher et al, 1984;Smith and Lefebvre, 1996] PF20 63-kDa WD-repeat containing protein that localizes to the inter-microtubule bridge connecting C1 and C2; pf20 flagella lack the entire central apparatus and are paralyzed [Adams et al, 1981;Smith and Lefebvre, 1997a] PP1c Localized primarily, but not exclusively, to the C1 microtubule [Yang et al, 2001] KLP1 83-kDa kinesin-like protein that localizes to the C2 microtubule [Bernstein et al, 1994] KRP 110-kDa kinesin related protein associated with the central apparatus, most likely the C1 microtubule [Fox et al, 1994;Johnson et al, 1994;Mitchell and Sale, 1999] AKAP240 240-kDa A-kinase anchoring protein; most likely associated with C2 [Gaillard et al, 2001] Calmodulin Most likely associated with C1, sediments as a complex at 10S [Yang et al, 2001;Dymek et al, 2002] Radial spoke-associated polypeptides RSP2 PF24 gene product, GAF, and calmodulin binding domain; pf24 mutants lack radial spoke heads and have paralyzed flagella Piperno et al, 1981;Yang et al, 2002] RSP3 PF14 gene product, 97-kDa A-kinase anchoring protein most likely localized to the base of the spokes; pf14 mutants lack radial spokes and have paralyzed flagella Piperno et al, 1981;Diener et al, 1993;Gaillard et al, 2001] RSP4 PF1 gene product, 49.8-kDa proline rich polypeptide similar to RSP6, pf1 mutants lack spoke heads and have paralyzed flagella Piperno et al, 1981;Curry et al, 1992] RSP6 PF26 gene product, 48.8-kDa proline rich polypeptide similar to RSP4, pf26 mutants lack spoke heads and have paralyzed flagella Piperno et al, 1981;Curry et al, 1992] LC8 RSP2...…”