The mouse Fau gene: genomic structure, chromosomal localization, and characterization of two retropseudogenes

Proteostasis regulated by testis-specific ribosomal protein RPL39L maintains mouse spermatogenesis

Maintaining proteostasis is important for animal development. How proteostasis influences spermatogenesis that generates male gametes, spermatozoa, is not clear. We show that testis-specific paralog of ribosomal large subunit protein RPL39, RPL39L, is required for mouse spermatogenesis. Deletion of Rpl39l in mouse caused reduced proliferation of spermatogonial stem cells, malformed sperm mitochondria and flagella, leading to sub-fertility in males. Biochemical analyses revealed that lack of RPL39L deteriorated protein synthesis and protein quality control in spermatogenic cells, partly due to reduced biogenesis of ribosomal subunits and ribosome homeostasis. RPL39/RPL39L is likely assembled into ribosomes via H/ACA domain containing NOP10 complex early in ribosome biogenesis pathway. Furthermore, Rpl39l null mice exhibited compromised regenerative spermatogenesis after chemical insult and early degenerative spermatogenesis in aging mice. These data demonstrate that maintaining proteostasis is important for spermatogenesis, of which ribosome homeostasis maintained by ribosomal proteins coordinates translation machinery to the regulation of cellular growth.

•

Rpl39l deletion causes reduced spermatogenesis and subfertility in male mice

•

SSC proliferation, mitochondria and sperm flagella compromised in Rpl39l^–/– mice

•

Rpl39l deletion affects ribosomal LSU formation and protein quality control

•

Aberrant proteostasis affects spermatogenesis and regeneration

Regulation of apoptosis by fau revealed by functional expression cloning and antisense expression

Functional expression cloning is a powerful strategy for identifying critical steps in biological pathways independently of prior assumptions. It is particularly suitable for the identification of molecules crucial to the control of apoptosis. Our screen for sequences suppressing T-cell apoptosis isolated a sequence antisense to fau (Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV)-associated ubiquitously expressed gene). The fox gene in FBR murine osteosarcoma virus is also antisense to fau and several reports have indicated that fau displays tumour suppressor and oncogenic properties in different contexts. Our observations indicate that the fau antisense sequence suppresses expression of endogenous fau mRNA and produces resistance to apoptosis induced both by the glucocorticoid analogue dexamethasone' by ultraviolet radiation, and by the anticancer drug cisplatin. In all cases, colony-forming ability is protected, indicating that fau affects the critical events prior to commitment to cell death. Overexpression of fau in the sense orientation induces cell death, which is inhibited both by Bcl-2 and by inhibition of caspases, in line with its proposed role in apoptosis.

Differential expression of bikunin (HAI-2/PB), a proposed mediator of glioma invasion, by demethylation treatment

Effective therapies for primary brain tumors continue to be elusive. Successful adjuvant therapies for CNS tumors will require a better understanding of their basic biology. Hepatocyte growth factor activator inhibitor type-2/placental bikunin (HAI-2/PB) is a serine proteinase inhibitor that has a broad inhibitory spectra against various serine proteinases. HAI-2/PB has anti-invasive effects thought to be mediated primarily by the inhibitory activity against serine proteinase-dependent matrix degradation. It has been previously demonstrated that the expression of HAI-2/PB is inversely related to degree of malignancy and possibly involved in the progression and invasion of human gliomas. Aberrant methylation patterns are an early change in glioma tumorigenesis, earlier than genetic changes. Methylation within 5' regulatory CpG islands by DNA methyltransferase is one of the most common epigenetic modifications. 5-Aza-2'-deoxycytidine (azacytidine) inhibits DNA methyltransferase and has been used in vitro to induce the expression of genes silenced by methylation. We have utilized azacytidine treatment and a micro-array system to investigate methylation influenced gene expression across several tumor cell lines of different lineage (brain, breast, prostate, liver). Using this system we have demonstrated that the expression of HAI-2/PB is under methylation control to a variable extent in glioma cell lines, in comparison to the other tested cell lines. Because the expression of HAI-2/B is inversely related to glioma invasiveness and degree of malignancy, this finding may provide insight into glioma initiation and progression as well as potentially providing new therapeutic targets.