Human and mouse ZFY genes produce a conserved testis-specific transcript encoding a zinc finger protein with a short acidic domain and modified transactivation potential

Abstract

Mammalian ZFY genes are located on the Y chromosome, and code putative transcription factors with 12–13 zinc fingers preceded by a large acidic (activating) domain. In mice, there are two genes, Zfy1 and Zfy2, which are expressed mainly in the testis. Their transcription increases in germ cells as they enter meiosis, both are silenced by meiotic sex chromosome inactivation (MSCI) during pachytene, and Zfy2 is strongly reactivated later in spermatids. Recently, we have shown that mouse Zfy2, but not Zfy1, is involved in triggering the apoptotic elimination of specific types of sex chromosomally aberrant spermatocytes. In humans, there is a single widely transcribed ZFY gene, and there is no evidence for a specific role in the testis. Here, we characterize ZFY transcription during spermatogenesis in mice and humans. In mice, we define a variety of Zfy transcripts, among which is a Zfy2 transcript that predominates in spermatids, and a Zfy1 transcript, lacking an exon encoding approximately half of the acidic domain, which predominates prior to MSCI. In humans, we have identified a major testis-specific ZFY transcript that encodes a protein with the same short acidic domain. This represents the first evidence that ZFY has a conserved function during human spermatogenesis. We further show that, in contrast to the full acidic domain, the short domain does not activate transcription in yeast, and we hypothesize that this explains the functional difference observed between Zfy1 and Zfy2 during mouse meiosis.

Mouse Y-Linked Zfy1 and Zfy2 Are Expressed during the Male-Specific Interphase between Meiosis I and Meiosis II and Promote the 2nd Meiotic Division

“…Recently we have shown that in the adult testis this transcription is limited to germ cells, starting in leptotene spermatocytes, with more robust transcription in zygotene spermatocytes, followed by silencing in pachytene spermatocytes as a consequence MSCI; there was no resumption of transcription prior to MI, but transcription was shown to have resumed in (Y-bearing) round spermatids [7]. However, no data are available for interphasic secondary spermatocytes [14].…”

“…Zfy1 and Zfy2 have the same predicted DNA target sequences, so if both are robustly expressed during zygotene, why is the apoptotic role limited to Zfy2 ? A plausible explanation is provided by our finding that during the pre-pachytene phase of transcription, alternative splicing of Zfy transcripts leads to ∼81% of Zfy1 transcripts lacking exon 6 with the encoded protein lacking transactivation (TA) activity, whereas ∼96% of Zfy2 transcripts have exon 6 and thus a functional TA domain [7]. Our current TA domain analysis further demonstrates that the few full length Zfy1 transcripts that are produced during zygotene generate a protein with a much less potent TA domain than that of Zfy2 .…”

“…Focus then shifted onto Zfy1 and Zfy2 because the Δ Sxr-b deletion breakpoints lie within these two genes, creating a transcribed Zfy2/Zfy1 fusion gene with the encoded protein almost identical to that encoded by Zfy1 [7], [13]. Introducing an X-linked Zfy2 transgene into X E O Sry males reinstated the apoptotic response but addition of Zfy1 had no discernible effect [11].…”

The expression of Y-linked Zfy2 in XY mouse oocytes leads to frequent meiosis 2 defects, a high incidence of subsequent early cleavage stage arrest and infertility

“…Quantitation by qRT-PCR of Zfy1 transcripts with and without exon 6 from Zfy1 hi and Zfy1 lo transgenic ovaries was as described previously (Decarpentrie et al, 2012), with 7-week-old XX ovary and 15 dpp XY testis as negative and positive controls, respectively. All qRT-PCR reactions were carried out in triplicate per assay.…”

The Role of Number of Copies, Structure, Behavior and Copy Number Variations (CNV) of the Y Chromosome in Male Infertility

“…Here we recall two of these genes, for the sake of completeness ( Figure 2). Zinc finger protein, Y-linked (ZFY) is expressed in germline, and Leydig cells [139], and mice knockout for Zfy genes are infertile [140]; in addition, its function in somatic cells seems minor, if any [141]. Nonetheless, the lack of known mutations of this gene alone in infertile men does not allow confirming what it does in human spermatogenesis.…”