Chromatin remodelling initiation in spermatids: differences among human males

Abstract

SUMMARYDuring the last phase of spermatogenesis, called spermiogenesis, the nucleosome-based chromatin structure is replaced by a protamine-based DNA packaging. Not much is known about the chromatin remodelling involved in humans and animals. Here, we have investigated initiation of chromatin remodelling over seven probands of which five were diagnosed with non-obstructive azoospermia (NOA) and two with obstructive azoospermia (OA) (failed vaso-vasostomy patients with proven fertility prior to vasectomy, Johnsen scores ! 9). Chromatin remodelling was studied evaluating the presence of nucleosomes, histone H3, pre-protamine 2 and protamine 1. This approach was feasible since the local initiation of nucleosome eviction in the sub acrosomal domain, which was visible in alkaline nuclear spread preparations. The patterns of nucleosome and H3 loss were largely congruent. Nucleus wide incorporation of protamine 1 could already be observed at the late round spermatid stage. Both for nucleosome loss and for protamine 1 incorporation, there was distinct variation within and between probands. This did not relate to the efficiency of sperm production per meiocyte. Pre-protamine 2 was always confined to the subacrosomal domain, confirming the role of this area in chromatin remodelling.

The inherited methylome landscape is directly altered with paternal aging and associated with offspring neurodevelopmental disorders

“…As such, we postulated that the DMRs identified in APA sperm colocalized with regions of retained histones. During spermiogenesis, the majority of histones are exchanged for protamines, but as many as 15% of nucleosomes are retained in regions of high CpG density and enriched at loci of developmental importance, including developmental gene promoters, imprinted loci, and genes encoding miRNAs (de Vries et al., 2013; Hammoud et al., 2009). By comparing our findings to those putatively bound to retained histones, previously identified by ChIP data from Hammoud et al., 2009, a statistically significant enrichment of APA sperm DMR‐associated genes correlated with nucleosome retention.…”

Nuclear envelope remodelling during human spermiogenesis involves somatic B-type lamins and a spermatid-specific B3 lamin isoform

“…We nevertheless did detect a lamin B2 signal with a specific antibody in the spermatids of the T3 subject by immunofluorescence, but a semen sample was not available to us to check for the lamin B2 transcript. It is possible that the presence of lamin B2 in spermatids could vary between individuals, as has been suggested for other proteins (de Vries et al, 2013). The analysis of more biopsies should resolve this issue, although the near impossibility of obtaining both spermatozoa and a testicular biopsy for a normospermic man will make it difficult to know whether the lamin B2 found in Figure 5 Protein expression of B1 and B2 lamins by western blot analysis of human spermatozoa lysates.…”

A mutation study of sperm head shape and motility in the mouse: lessons for the clinic

“…In this region, specialized members of the linker of nucleoskeleton and cytoskeleton complex (LINC complex) functioning in communication between nucleoskeleton and cytoskeleton over the nuclear membranes, can be observed. Recently, it was discovered that the onset of nucleosome eviction, and the descend of the acrosomal sac onto the nucleus are coordinated in time (de Vries et al ., , ) suggesting a causative relation.…”

“…Also in the Prm2 knockout, the acrosome can be loosely attached to the nucleus and frequently appears irregular (Cho et al ., ). As pre‐P2 is found exclusively in and/or under the acrosome in human round and elongating spermatids (de Vries et al ., , ), the acrosome could be involved in chromatin processing in a way that is not yet understood. Recently, the polycomb repressive complex 2 protein H3K27 methyl transferase Ezh2 was found to localize in the acrosomal granule, providing, an additional argument for the involvement of the acrosome in chromatin processing (Lambrot et al ., ).…”