Characterization of the bovine leukocyte antigen (BoLA) DRB3 gene has shown that specific alleles associate with susceptibility or resilience to the progression of bovine leukemia virus (BLV), measured by proviral load (PVL). Through surveillance of multi-farm BLV eradication field trials, we observed differential phenotypes within seropositive cows that persist from months to years. We sought to develop a multiplex next-generation sequencing workflow (NGS-SBT) capable of genotyping 384 samples per run to assess the relationship between BLV phenotype and two BoLA genes. We utilized longitudinal results from milk ELISA screening and subsequent blood collections on seropositive cows for PVL determination using a novel BLV proviral load multiplex qPCR assay to phenotype the cows. Repeated diagnostic observations defined two distinct phenotypes in our study population, ELISA-positive cows that do not harbor detectable levels of provirus and those who do have persistent proviral loads. In total, 565 cows from nine Midwest dairy farms were selected for NGS-SBT, with 558 cows: 168 BLV susceptible (ELISA-positive/PVL-positive) and 390 BLV resilient (ELISA-positive/PVL-negative) successfully genotyped. Three BoLA-DRB3 alleles, including one novel allele, were shown to associate with disease resilience, *009:02, *044:01, and *048:02 were found at rates of 97.5%, 86.5%, and 90.3%, respectively, within the phenotypically resilient population. Alternatively, DRB3*015:01 and *027:03, both known to associate with disease progression, were found at rates of 81.1% and 92.3%, respectively, within the susceptible population. This study helps solidify the immunogenetic relationship between BoLA-DRB3 alleles and BLV infection status of these two phenotypic groupings of US dairy cattle.

Bovine leukemia virus (BLV) causes Enzootic Bovine Leukosis (EBL), a persistent life-long disease resulting in immune dysfunction and shortened lifespan in infected cattle, severely impacting the profitability of the US dairy industry. Our group has found that 94% of dairy farms in the United States are infected with BLV with an average in-herd prevalence of 46%. This is partly due to the lack of clinical presentation during the early stages of primary infection and the elusive nature of BLV transmission. This study sought to validate a near-complete genomic sequencing approach for reliability and accuracy before determining its efficacy in characterizing the sequence identity of BLV proviral genomes collected from a pilot study made up of 14 animals from one commercial dairy herd. These BLV-infected animals were comprised of seven adult dam/daughter pairs that tested positive by ELISA and qPCR. The results demonstrate sequence identity or divergence of the BLV genome from the same samples tested in two independent laboratories, suggesting both vertical and horizontal transmission in this dairy herd. This study supports the use of Oxford Nanopore sequencing for the identification of viral SNPs that can be used for retrospective genetic contact tracing of BLV transmission.

Chromatin remodeling plays an integral part in endometrial homeostasis through its roles in the maintenance of cell identity, epithelial integrity, and prevention of endometrial disease. Chromodomain-helicase-DNA-binding protein 4 (CHD4) is a chromatin remodeling protein and member of the NuRD complex, which predominantly represses transcription. CHD4 is mutated in endometrial carcinoma, with most mutations resulting in loss of function. CHD4 has been identified as a tumor suppressor and regulator of stemness in human endometrial carcinoma cell lines, but little is known about the tissue-specific roles of CHD4 in the endometrial epithelia in vivo. We generated a conditional Chd4 floxed allele and combined it with BAC-Sprr2f-Cre to drive CHD4 loss in the endometrial epithelium. Consistent with previous reports, BAC-Sprr2f-Cre shows variegated expression within the endometrial epithelium and lacks expression in the oviducts, ovaries, and kidneys. Loss of CHD4 was confirmed by immunohistochemistry, and the percentage of endometrial epithelial cells with and without CHD4 was quantified. Compared to the glandular epithelium, the extent of CHD4 loss was higher in the luminal epithelium and unaffected by age. Mice with conditional knockout of Chd4 had normal endometrial histology. A six-month breeding trial was performed to assess the functional effects of endometrial epithelial CHD4 loss on fertility and found no difference in litter size, average litter size per dam, or pup weight between genotypes. These findings demonstrate that Chd4 conditional knockout using BAC-Sprr2f-Cre is not sufficient to alter the structure and function of the endometrial epithelium or drive tumorigenesis. As CHD4 is frequently co-mutated with other cancer driver genes such as TP53 , PIK3CA , and PTEN , future mouse modeling efforts emulating patient mutational profiles might provide insight into the role of CHD4 in endometrial carcinoma.

Chromatin remodeling plays an integral part in endometrial homeostasis, having roles in the maintenance of cell identity, epithelial integrity, and prevention of endometrial disease. Chromodomain-helicase-DNA-binding protein 4 ( CHD4 ) is a chromatin remodeling protein and member of the NuRD complex, which predominantly represses transcription. CHD4 is mutated in endometrial carcinoma, with most mutations leading to loss of function. CHD4 has been identified as a tumor suppressor and regulator of stemness in endometrial carcinoma cells, but little is known about the tissue-specific roles of CHD4 in the endometrial epithelia in vivo. We generated a conditional Chd4 floxed allele and combined it with BAC-Sprr2f-Cre to drive Chd4 loss in the endometrial epithelium. Consistent with previous reports, BAC-Sprr2f-Cre expression is absent in the oviducts, ovaries, and kidneys, and it shows variegated expression within the endometrial epithelium. Loss of CHD4 was confirmed by immunohistochemistry, and stained cells were quantified to determine the percentage of endometrial epithelial cells with and without CHD4. Compared to the glandular epithelium, the extent of CHD4 loss was higher in the luminal epithelium and unaffected by age. Mice with conditional knockout of Chd4 had normal endometrial histology. A 6-month breeding trial was performed to assess the functional effects of endometrial epithelial Chd4 loss on fertility. No difference in litter size, mean number of pups per litter per dam, or pup weight was found between genotypes. These findings demonstrate that Chd4 conditional loss using BAC-Sprr2f-Cre is not sufficient to alter the structure and function of the endometrial epithelium or drive tumorigenesis. As CHD4 is frequently co-mutated with other cancer driver genes such as TP53 , PIK3CA , and PTEN , future mouse modeling efforts emulating patient mutational profiles might provide insight into the role of CHD4 in endometrial carcinoma.