Lsh/HELLS is required for B lymphocyte development and immunoglobulin class switch recombination

Abstract

Mutation of HELLS (Helicase, Lymphoid-Specific)/Lsh in human DNA causes a severe immunodeficiency syndrome, but the nature of the defect remains unknown. We assessed here the role of Lsh in hematopoiesis using conditional Lsh knockout mice with expression of Mx1 or Vav Cre-recombinase. Bone marrow transplantation studies revealed that Lsh depletion in hematopoietic stem cells severely reduced B cell numbers and impaired B cell development in a hematopoietic cell-autonomous manner. Lsh-deficient mice without bone marrow transplantation exhibited lower Ig levels in vivo compared to controls despite normal peripheral B cell numbers. Purified B lymphocytes proliferated normally but produced less immunoglobulins in response to in vitro stimulation, indicating a reduced capacity to undergo class switch recombination (CSR). Analysis of germline transcripts, examination of double-stranded breaks using biotin-labeling DNA break assay, and End-seq analysis indicated that the initiation of the recombination process was unscathed. In contrast, digestion–circularization PCR analysis and high-throughput sequencing analyses of CSR junctions and a chromosomal break repair assay indicated an impaired ability of the canonical end-joining pathway in Lsh-deficient B cells. Our data suggest a hematopoietic cell-intrinsic role of Lsh in B cell development and in CSR providing a potential target for immunodeficiency therapy.

The epigenetic regulator LSH maintains fork protection and genomic stability via MacroH2A deposition and RAD51 filament formation

“…1e ). Genomic instability, however, was not associated with substantial increases in cell death, since LSH-deficient B cells display no significant differences in cellular growth and survival rates in vitro when compared to LSH-proficient cells 14 . Altogether, our data revealed increased signs of DNA damage and genomic instability in proliferating LSH-deficient lymphocytes.…”

“…We used conditional Lsh knockout mice with Lsh gene depletion in the hematopoietic system to investigate signs of genomic instability in LSH-KO and control lymphocytes (Supplementary Fig. 1a ) 14 . Using immunofluorescence analysis, we found that LSH-deficient lymphocytes, stimulated with either B (Fig.…”

“…Splenocytes were derived from Cre-recombinase-mediated conditional deletion of Lox-P site flanked (“floxed”) Lsh gene 14 . Splenocytes were cultured in Roswell Park Memorial Institute (RPMI) 1640 Medium (Thermo Fisher Scientific) supplemented with 10% fetal bovine serum (FBS; Omega Scientific), 25 µg/ml lipopolysaccharide (LPS) (Sigma Aldrich) and standard antibiotics.…”

The DNA-helicase HELLS drives ALK− ALCL proliferation by the transcriptional control of a cytokinesis-related program

“…HELLS is a multifunctional protein proved to play, among the others, critical roles in DNA methylation, chromatin packaging, and development of lymphoid tissue 47 . Known also as Lymphoid-specific helicase (Lsh) HELLS is required for normal development and survival of lymphoid and other tissues via chromatin organization 48 49 , promotion of DNA double-strand break repair 50 , 51 and chromatin accessibility modification 52 , 53 . In cancer, HELLS is deregulated in several settings i.e.…”

Chromatin remodeling in replication‐uncoupled maintenance DNA methylation and chromosome stability: Insights from ICF syndrome studies

“…We revealed that this complex facilitates the nonhomologous end joining (NHEJ) of double-strand breaks (DSBs) by enhancing access of Ku80 (also called XRCC5), a factor essential for NHEJ by protecting DSB ends from resection, to the sites of DSBs, and potentially suppresses many cytological defects; ZBTB24 KO, CDCA7 KO, and HELLS KO human embryonic kidney 293 (HEK293) cells generated using the CRISPR/ Cas9 system displayed enlarged nuclei, centrosome amplification, abnormal chromosome segregation, and many related phenotypes, including proliferation defects, aneuploidy, and apoptosis (Unoki et al, 2019). Recently, it was reported that ZBTB24 and HELLS are essential for NHEJ during immunoglobulin class-switch recombination (He et al, 2020;Helfricht et al, 2020). Taken together, these findings indicate that ZBTB24, CDCA7, and HELLS are largely involved in the same biological pathway, although they also have their specific functions; for example, (Jarvis et al, 1996) Genes to Cells UNOKI ZBTB24 works not only as a transcriptional activator of CDCA7, but also as a direct regulator of poly(ADP-ribose) polymerase 1 (PARP1)-dependent NHEJ and class-switch recombination (Helfricht et al, 2020).…”