The reference OMIM entry for this protein is 300603

Actin-binding protein, 34-kd
Pof1b gene; pof1b

CLONING

Bione et al. (2004) identified a gene, which they called POF1B, by fine mapping of the X chromosome breakpoint of an X;autosome balanced translocation in a patient with premature ovarian failure (POF; see 311360) reported by Riva et al. (1996). The breakpoint in the patient occurred in the distal 4 kb of the third intron of the gene.

GENE FUNCTION

Bione et al. (2004) determined that Pof1B expression is absent from adult mouse ovary but is present between embryonic day 16.5 and postnatal day 5, suggesting that the gene may be critical for the steps required for early ovary development leading to the final number of germ cells. By RT-PCR amplification of total RNA from 5 human-hamster hybrid cell lines containing only the inactive human X chromosome, Bione et al. (2004) determined that the POF1B gene escapes X inactivation. Southern blot analysis excluded the presence of a homolog on the Y chromosome. Lacombe et al. (2006) performed protein sequence comparisons against different databases to investigate the function of POF1B, the results of which suggested that POF1B shares homology with the myosin tail portion of the human myosin protein. Because of this homology, Lacombe et al. (2006) assessed the ability of both wildtype and mutant POF1B proteins to bind nonmuscle actin filaments in vitro. They found that the capacity of the mutant protein to bind nonmuscle actin filaments was diminished 4-fold compared with wildtype, suggesting a function of POF1B in germ cell division.

GENE STRUCTURE

Bione et al. (2004) determined that the POF1B gene contains 17 exons spanning a region of more than 100 kb.

MAPPING

By breakpoint analysis in a patient with a balanced X;1 translocation, Bione et al. (2004) mapped the POF1B gene to chromosome Xq21.

MOLECULAR GENETICS

Bione et al. (2004) considered the POF1B gene a candidate for premature ovarian failure because it is located within the critical region for normal ovarian function, escapes X inactivation, and a breakpoint in the third intron was identified in a POF patient with an X;1 translocation (Riva et al., 1996). From a mutation analysis of POF1B performed in an Italian population, Bione et al. (2004) concluded that either the POF1B gene was not associated with POF, or its contribution could not be demonstrated in the very heterogeneous group of patients available to them. In a Lebanese family with POF showing linkage to Xq21, Lacombe et al. (2006) identified a point mutation in exon 10 of the POF1B gene (300603.0001). The authors also determined that mutant POF1B bound nonmuscle actin with less affinity than wildtype POF1B in vitro. Lacombe et al. (2006) speculated that the POF1B protein is involved in actin-filament interaction and that the R329Q variant leads to a lack of phosphorylation at the serine-leucine-arginine site, which causes the loss of function of the POF1B protein. Based on its expression pattern in mouse development (Bione et al., 2004), Lacombe et al. (2006) also hypothesized that POF1B could play a role in the pairing of meiotic chromosomes and that alteration in its function could lead to cell death and a drastic reduction in the final number of oocytes created during ovarian development. Alternatively, POF1B may act as an antiapoptosis factor, to slow down the process of germ cell loss; as a consequence, loss of function of POF1B could lead to exaggerated germ cell apoptosis and POF. ... More on the omim web site

Subscribe to this protein entry history

Dec. 10, 2018: Protein entry updated
Automatic update: model status changed

Nov. 17, 2018: Protein entry updated
Automatic update: OMIM entry 300603 was added.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).