Drosophila Dynein Intermediate Chain Gene, Dic61B, Is Required for Spermatogenesis

Abstract

This study reports the identification and characterization of a novel gene, Dic61B, required for male fertility in Drosophila. Complementation mapping of a novel male sterile mutation, ms21, isolated in our lab revealed it to be allelic to CG7051 at 61B1 cytogenetic region, since two piggyBac insertion alleles, CG7051c05439 and CG7051f07138 failed to complement. CG7051 putatively encodes a Dynein intermediate chain. All three mutants, ms21, CG7051c05439 and CG7051f07138, exhibited absolute recessive male sterility with abnormally coiled sperm axonemes causing faulty sperm individualization as revealed by Phalloidin staining in Don Juan-GFP background. Sequencing of PCR amplicons uncovered two point mutations in ms21 allele and confirmed the piggyBac insertions in CG7051c05439 and CG7051f07138 alleles to be in 5′UTR and 4th exon of CG7051 respectively, excision of which reverted the male sterility. In situ hybridization to polytene chromosomes demonstrated CG7051 to be a single copy gene. RT-PCR of testis RNA revealed defective splicing of the CG7051 transcripts in mutants. Interestingly, expression of cytoplasmic dynein intermediate chain, α, β, γ tubulins and α-spectrin was normal in mutants while ultra structural studies revealed defects in the assembly of sperm axonemes. Bioinformatics further highlighted the homology of CG7051 to axonemal dynein intermediate chain of various organisms, including DNAI1 of humans, mutations in which lead to male sterility due to immotile sperms. Based on these observations we conclude that CG7051 encodes a novel axonemal dynein intermediate chain essential for male fertility in Drosophila and rename it as Dic61B. This is the first axonemal Dic gene of Drosophila to be characterized at molecular level and shown to be required for spermatogenesis.

Separating from the pack: Molecular mechanisms ofDrosophilaspermatid individualization

“…42,43 Furthermore, the putative axonemal Dynein Intermediate Chain Dic61B is required for individualization. 44 However, other studies suggest that individualization can occur normally in the absence of certain axonemal components. 45 Finally, DDLC1 plays a role in actin accumulation on the cones, which is independent of the Dynein-Dynactin motor and could result from its association with Myosin V. 34,46 The individualization process may require deposition of new membrane between the spermatids.…”

Whole-Organ Isolation Approach as a Basis for Tissue-Specific Analyses in Schistosoma mansoni

“…Further target genes (SmAQP, SmSPRM1hc, SmNPP-5) were shown to be preferentially, but not exclusively localised in the tegument of adult worms [82], [72], [83]. Additionally, SmHSP70 was chosen as it had been detected throughout diverse life stages and tissues as well as SmAxDynIC, which was expected to be expressed in testes due to its predicted function in sperm axonemes ([84], Table 1). As expected, most of the analysed target genes were transcribed in testes, ovaries, and adult couples, whereas the nucleotide pyrophosphatase/phosphodiesterase SmNPP-5 was not detected in the reproductive organs.…”

“…Axonemal dynein intermediate chains have been described to function in cilia and flagella as well as in sperm axoneme assembly being important for spermatogenesis and fertility [84], [97]. Accordingly, SmAxDynIC transcripts were detected in testes but not in ovaries by organ-specific RT-PCRs and consequently could serve as a testes-specific marker.…”

Genomics of parallel adaptation at two timescales in Drosophila

“…For example, Dic61B codes for an axonemal dynein intermediate chain exhibiting strong testis-biased expression (FlyBase); it is required for development and precise assembly of sperm axonemes and is essential for male fertility in D . melanogaster [87,88]. Given the rapid evolution of sperm length in D .…”