Pleomorphic adenoma gene1 in reproduction and implication for embryonic survival in cattle: a review

The pleomorphic adenoma gene1 (PLAG1) encodes a DNA-binding, C2H2 zinc-finger protein which acts as a transcription factor that regulates the expression of diverse genes across different organs and tissues; hence, the name pleomorphic. Rearrangements of the PLAG1 gene, and/or overexpression, are associated with benign tumors and cancers in a variety of tissues. This is best described for pleomorphic adenoma of the salivary glands in humans. The most notable expression of PLAG1 occurs during embryonic and fetal development, with lesser expression after birth. Evidence has accumulated of a role for PLAG1 protein in normal early embryonic development and placentation in mammals. PLAG1 protein influences the expression of the ike growth factor 2 (IGF2) gene and production of IGF2 protein. IGF2 is an important mitogen in ovarian follicles/oocytes, embryos, and fetuses. The PLAG1-IGF2 axis, therefore, provides one pathway whereby PLAG1 protein can influence embryonic survival and pregnancy. PLAG1 also influences over 1,000 other genes in embryos including those associated with ribosomal assembly and proteins. Brahman (Bos indicus) heifers homozygous for the PLAG1 variant, rs109815800 (G > T), show greater fertility than contemporary heifers with either one, or no copy, of the variant. Greater fertility in heifers homozygous for rs109815800 could be the result of early puberty and/or greater embryonic survival. The present review first looks at the broader roles of the PLAG1 gene and PLAG1 protein and then focuses on the emerging role of PLAG1/PLAG1 in embryonic development and pregnancy. A deeper understanding of factors which influence embryonic development is required for the next transformational increase in embryonic survival and successful pregnancy for both in vivo and in vitro derived embryos in cattle.

Pleomorphic adenoma gene 1 (PLAG1) promotes proliferation and inhibits apoptosis of bovine primary myoblasts through the PI3K-Akt signaling pathway

Pleomorphic adenoma gene 1 (PLAG1) is a transcription factor involved in various cellular processes in organismal growth and development. However, its role in muscle function is unclear. This work investigated the roles of PLAG1 in muscle development and explored its regulatory mechanisms. The PLAG1 was proved to promote the proliferation of bovine primary myoblasts using the cell counting kit 8 (CCK-8) assay (P < 0.001), 5-ethynyl-2'-deoxyuridine (EdU) proliferation assay (P = 0.005), quantitative real-time polymerase chain reaction (qRT-PCR) (P = 0.028), western blot, and flow cytometry (P < 0.05), and to inhibit apoptosis of bovine primary myoblasts using qRT-PCR (P = 0.038), western blot, and flow cytometry (P < 0.001). Chromatin immunoprecipitation sequencing (ChIP-seq) and western blot showed PLAG1 upregulated phosphorylated (p)-PI3K, PI3K, p-Akt, Akt, Cyclin D1, and CDK2 and inhibited the expression of p21 and p27 to enhance myoblast proliferation, and increased expression of Bcl-2, and Bcl-xL to inhibit apoptosis. Additionally, PLAG1 was identified as a target of miR-1 using dual-luciferase assay (P < 0.001), qRT-PCR (P < 0.001), and western blot. Furthermore, miR-1 might be a potential mediator of the positive feedback regulation relationship between PLAG1 and the PI3K-Akt signaling pathway.

Genetic variation in PLAG1 is associated with early fertility in Australian Brahman cattle

Variation in the genome region coding for PLAG1 has well-documented associations with skeletal growth and age at puberty in cattle. However, the influence of PLAG1 on other economically important traits such as cow stayability has not yet been explored. Here we investigate the effect of PLAG1 variation on early and later in life female fertility, as well as size and growth, in a well phenotyped Australian Brahman herd. Yearly pregnancy and productivity records were collected from 2,839 genotyped Brahman cows and used to generate fertility, growth, and weight phenotypes. A variant on chromosome 14 in PLAG1 (NC_037341.1:g.23338890G>T, rs109815800) was previously determined to be a putative causative mutation associated with variation in cattle stature. The imputed PLAG1 genotype at this variant was isolated for each animal and the effect of PLAG1 genotype on each trait was estimated using linear modelling. Regardless of how heifer fertility was measured, there was a significant (P < 0.05) and desirable relationship between the additive effects of PLAG1 genotype and successful heifer fertility. Heifers with two copies of the alternate allele (TT) conceived earlier and had higher pregnancy and calving rates. However, the effects of PLAG1 genotype on fertility began to diminish as cows aged and did not significantly influence stayability at later ages. While there was no effect of genotype on growth, PLAG1 had a negative effect on mature cow weight (P < 0.01), where females with two copies of the alternate allele (TT) were significantly smaller than those with either one or none. Selection emphasis on improved Brahman heifer fertility will likely increase the frequency of the T allele of rs109815800, which may also increase herd profitability and long-term sustainability through improved reproductive efficiency and reduced mature cow size.

Giant Cell Carcinosarcoma of the Parotid Gland With a PLAG 1 Translocation in Association With a Pleomorphic Adenoma With HMGA2 Translocation

OBJECTIVES

Carcinosarcomas of the salivary gland are rare neoplasms and have been described arising de novo or in association with pleomorphic adenoma (PA). PLAG1 and HMGA2 translocations are known to occur in PAs and carcinomas ex PA but are mutually exclusive.

METHODS

We report a case of a carcinosarcoma in the parotid gland of a 77-year-old man with unusual anaplastic sarcomatoid giant cell morphology.

RESULTS

Microscopically, a small separate PA was found adjacent to the carcinosarcoma. By conventional notion, the PA and carcinosarcoma would be considered related, as carcinosarcomas are well known to arise from PAs (carcinosarcoma ex PA). However, fluorescence in situ hybridization (FISH) assay demonstrated PLAG1 translocation in the carcinosarcoma and HMGA2 translocation in the separate PA.

CONCLUSIONS

These findings support that the carcinosarcoma likely originated from another PA with a PLAG1 translocation or de novo but not from the coexisting PA harboring a different translocation. To our knowledge, the case is the first to demonstrate PLAG1 translocation by FISH in a sarcomatous component of any parotid gland tumor, which may help better classify these tumors. In addition, multiple PAs are commonly found in the salivary gland, and to our knowledge, our case is the first to demonstrate that the same parotid gland can host PAs and PA-related tumors with different translocations.