A missense in HSF2BP causing Primary Ovarian Insufficiency affects meiotic recombination by its novel interactor C19ORF57/MIDAP

Abstract

Felipe-Medina et al. describe a missense variant in the meiotic gene HSF2BP in a consanguineous family with Premature Ovarian Insufficiency, and characterize it as an hypormorphic allele, that in vivo impairs its dimerization with a novel meiotic actor, MIDAP/ C19ORF57, and affect recombination at double-strand DNA breaks. AbstractPrimary Ovarian Insufficiency (POI) is a major cause of infertility, but its etiology remains poorly understood. Using whole-exome sequencing in a family with 3 cases of POI, we identified the candidate missense variant S167L in HSF2BP, an essential meiotic gene.Functional analysis of the HSF2BP-S167L variant in mouse, compared to a new HSF2BP knock-out mouse showed that it behaves as a hypomorphic allele. HSF2BP-S167L females show reduced fertility with small litter sizes. To obtain mechanistic insights, we identified C19ORF57/MIDAP as a strong interactor and stabilizer of HSF2BP by forming a higherorder macromolecular structure involving BRCA2, RAD51, RPA and PALB2. Meiocytes bearing the HSF2BP-S167L mutation showed a strongly decreased expression of both MIDAP and HSF2BP at the recombination nodules. Although HSF2BP-S167L does not affect heterodimerization between HSF2BP and MIDAP, it promotes a lower expression of both proteins and a less proficient activity in replacing RPA by the recombinases RAD51/DMC1, thus leading to a lower frequency of cross-overs. Our results provide insights into the molecular mechanism of two novel actors of meiosis underlying non-syndromic ovarian insufficiency.

Chromosome Pairing Through Tensioned DNA Tethers Revealed by BRCA2 Meiotic Domain Deletion

“…In the mutant, RPA foci were present and the number was increased compared to wild type (Figure 2D,E), suggesting that DSBs can be formed, but that RPA cannot be replaced by recombinases. Also, the foci numbers of SPATA22, a meiosis-specific single-stranded DNA binding protein [34][35][36] , were higher in absence of exons 12-14 of Brca2 than in the controls (Figure 2D,F), similar to what was observed in Hsf2bp -/and Brme1 -/spermatocytes 19,25,27,28 . Since the Brca2 ∆12-14 mouse model completely lacks the HSF2BP-binding domain, we investigated the localization patterns of HSF2BP and its interaction partner BRME1.…”

“…As exon 12 boundaries fall in the same position relative to the reading frame, this deletion did not lead to a frame shift. The Brca2 ∆12 mice were phenotypically normal and fertile, in contrast to the male sterility of the Hsf2bp knockout 19,21,25 . This put the role of HSF2BP-BRCA2 interaction in meiotic HR into question.…”

“…Mice deficient for HSF2BP are born at Mendelian ratios and have no overt somatic phenotypes, but males are infertile due to meiotic HR failure. Shortly after, HSF2BP was shown to directly interact with another uncharacterized protein named BRME1 (also called MAMERR or MEIOK21), and the phenotypes of the Hsf2bp and Brme1 knockout mouse models 19,21,[25][26][27][28][29] were similar.…”

“…Hsf2bp -/and Brme1 -/mice showed a sexual dimorphism regarding defects in meiosis 19,21,[25][26][27][28][29]37 . Therefore, we also analyzed meiotic HR protein localization patterns in embryonic (E15.5 and E17.5) Brca2 ∆12-14 oocyte nuclei, since female meiotic prophase initiates during embryogenesis.…”

Meiosis-Specific C19orf57/4930432K21Rik/BRME1 Modulates Localization of RAD51 and DMC1 to DSBs in Mouse Meiotic Recombination

“…It should be mentioned that our Brme1 KO male mice were subfertile, whereas those from the other group were completely infertile (Felipe-Medina et al, 2020). Although our Brme1 KO mice had a larger deletion encompassing exons 3-9 in the Brme1 locus, which corresponded to almost the entire protein coding sequence, resulting in complete null allele (Figure 2A), those from the other group had 40-bp deletion at exon 6, which was predicted to cause a frameshift mutation.…”