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dBigH1 - the histone H1 variant essential for spermatogenesis

Researchers of the IBMB have identified the crucial role of the germline-specific histone dBigH1.

Researchers of the IBMB have identified the crucial role of the germline-specific histone dBigH1, in the development of male sex cells from germ stem cells. The work has been performed in Drosophila melanogaster and sheds light on the functional requirement of the germline-specific histones to ensure male fertility. dBigH1 expression is successively turned on and off during spermatogenesis. This tightly regulated expression is crucial because, when it is expressed, dBigH1 represses specific genes that control the differentiation of the germ stem cells. When this delicate balance is lost, male Drosophila melanogaster shows gonadal malformations and infertility.

Linker histone H1s interact with the nucleosome and regulate chromatin compaction. In comparison to core histones, H1s are less evolutionarily conserved, and most species present several variants. A common feature of most of the multicellular animals is the presence of H1 variants that replace somatic H1s in the germline. Vertebrates generally contain several male-specific variants and one female-specific H1. Little is known about the functions that germline-specific H1s play in differentiation of the germ stem cells. In contrast, Drosophila presents a single germline-specific histone dBigH1, which is expressed in both the female and the male germline. In this regard, this work gives important insights into the function of germline-specific H1s by describing the mechanism of action and regulation of dBigH1 to ensure correct spermatogenesis. Our results suggest that dBigH1 is essential for germ stem cell maintenance and differentiation. dBigH1 acts as a general silencing factor that represses Bam, a key regulator of the first stages of spermatogenesis. Reciprocally, Bam represses dBigH1 and this double-repressor mechanism is crucial for the correct differentiation of the germ stem cells.

 

This research has been performed by the ‘Chromatin Structure and Function’ group (Dr. Ferran Azorín) of the IBMB, and has been published in Cell Reports.

 

Carbonell A, Pérez-Montero S, Climent-Cantó P, et al. The Germline Linker Histone dBigH1 and the Translational Regulator Bam Form a Repressor Loop Essential for Male Germ Stem Cell Differentiation. Cell reports.21(11):3178-3189. doi: 10.1016/j.celrep.2017.11.060.

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