Description

Description

The odd-skipped family of transcription factors are involved in a wide variety of developmental pathways across many taxa (Tena et al. 2007; Wang et al. 2005; Coulter et al. 1990). The genome of C. elegans encodes two odd genes, odd-1 and odd-2. A deletion mutant that deletes the transcription start site of the odd-2 gene has been classified as larval lethal by the National BioResource Project (https://nbrp.jp/en/). Early larval lethality was also seen with odd-2 injection RNAi, due to defects of the developing gut (Buckley et al. 2004). Buckley et al. also reported larval lethality with odd-1 injection RNAi, but only with the full-length construct that also has high homology to the zinc finger region of odd-2. When a smaller construct that did not contain the zinc-finger region was used, lethality was not seen (Buckley et al. 2004). Buckley et al. observed gut expression in embryos and early larvae using a 2 fragment GFP co-injection method and an integrated array. However, due to silencing of expression from multicopy arrays, it is unknown whether odd-1 expresses in the germline. Mammals have two odd-skipped genes, odd-skipped-related 1 and 2 (OSR1 and 2). A phylogenetic tree based on the zinc finger region of the protein shows that odd-2 is most closely related to both mammalian genes, while odd-1 is more distantly related (Buckley et al. 2004). However, one of the human genes, OSR2, is most highly expressed in somatic and germline tissues related to reproduction, including uterus, vagina, cervix, Fallopian tube, ovary and testis (GTEx Consortium 2013). As a first step to clarifying the role of odd-1 in the life cycle and development of C. elegans, we analyzed brood size of an odd-1(tm848) complex substitution (Figure 1A). This substitution consists of an 809 bp deletion and a 3 bp insertion in the 989 bp odd-1 transcript. Of the 242 amino acids in ODD-1, the N-terminal 45 amino acids are intact, as are the last 14, and one amino acid is inserted. All three predicted zinc fingers (Buckley et al. 2004) are deleted. This mutation is a putative null, because ODD-1 would not be able to bind DNA in a site-specific manner, although it is possible that there is a function for the remaining portion of the protein. FX848 was outcrossed five times (to create strain ACG4) and then assayed for brood size. Three brood size experiments were conducted; each recorded the brood sizes of five wild-type and five odd-1(tm848) worms. No significant difference was found in brood size (P=0.65), with an average wild-type brood size of 307 ±38 and an average mutant brood size of 301 ±33 (Figure 1B). The number of offspring in odd-1 mutant worms is comparable to that of wild-type worms, indicating no obvious phenotypes affecting gamete production, egg laying or embryonic development. Additionally, no obvious early larval lethality was seen during the course of the brood size experiments, as the offspring counted on day three were generally late larvae/early adults. While low levels of lethality may be uncovered by performing a dedicated lethality assay, odd-1(tm848) does not appear to cause widespread early larval lethality, as was reported for injection RNAi of full-length odd-1 (Buckley et al. 2004).