Evolutionarily conserved clusters of colon with lung cancer susceptibility loci, linked with most DUSP phosphatase genes, may help to dissect mechanisms of cancer susceptibility

We show evolutionarily conserved pairwise genetic linkage and clustering of majority of colon and lung cancer susceptibility QTLs in mice, rats and humans. The patterns of susceptibility or resistance to these two cancers in recombinant congenic mouse strains were concordant and the responsible susceptibility loci closely linked, in spite of completely different carcinogens and protocols used for induction of the two tumors. Most DUSP (Dual specificity phosphatase) genes are linked to these clusters. These data suggest that an important part of colon and lung cancer susceptibility is controlled by related and evolutionarily conserved processes.

Deep Sequencing of MHC-Adapted Viral Lines Reveals Complex Recombinational Exchanges With Endogenous Retroviruses Leading to High-Frequency Variants

Experimental evolution (serial passage) of Friend virus complex (FVC) in mice demonstrates phenotypic adaptation to specific host major histocompatibility complex (MHC) genotypes. These evolved viral lines show increased fitness and virulence in their host-genotype-of-passage, but display fitness and virulence tradeoffs when infecting unfamiliar host MHC genotypes. Here, we deep sequence these viral lines in an attempt to discover the genetic basis of FVC adaptation. The principal prediction for genotype-specific adaptation is that unique mutations would rise to high frequency in viral lines adapted to each host MHC genotype. This prediction was not supported by our sequencing data as most observed high-frequency variants were present in each of our independently evolved viral lines. However, using a multi-variate approach to measure divergence between viral populations, we show that populations of replicate evolved viral lines from the same MHC congenic mouse strain were more similar to one another than to lines derived from different MHC congenic mouse strains, suggesting that MHC genotype does predictably act on viral evolution in our model. Sequence analysis also revealed rampant recombination with endogenous murine leukemia virus sequences (EnMuLVs) that are encoded within the BALB/c mouse genome. The highest frequency variants in all six lines contained a 12 bp insertion from a recombinant EnMuLV source, suggesting such recombinants were either being favored by selection or were contained in a recombinational hotspot. Interestingly, they did not reach fixation, as if they are low fitness. The amount of background mutations linked to FVC/EnMuLV variable sites indicated that FVC/EnMuLV recombinants had not reached mutation selection equilibrium and thus, that EnMuLV sequences are likely continuously introgressing into the replicating viral population. These discoveries raise the question: is the expression of EnMuLV sequences in mouse splenocytes that permit recombination with exogenous FVC a pathogen or host adaptation?

Phosphorylation of STIM1 at ERK/CDK sites is dispensable for cell migration and ER partitioning in mitosis

Store-operated Ca2+ entry (SOCE) is a ubiquitous Ca2+ influx required for multiple physiological functions including cell motility. SOCE is activated in response to depletion of intracellular Ca2+ stores following the activation of endoplasmic reticulum (ER) Ca2+ sensor STIM1 which recruits the plasma membrane (PM) Ca2+ channel Orai1 at ER-PM junctions to induce Ca2+ influx. STIM1 is phosphorylated dynamically and this phosphorylation has been implicated in several processes including SOCE inactivation during M-phase, maximal SOCE activation, ER segregation during mitosis, and cell migration. STIM1 has 10 Ser/Thr residues in its cytosolic domain that match the ERK/CDK consensus phosphorylation. We recently generated a mouse knock-in line where wild-type STIM1 was replaced by a non-phosphorylatable STIM1 with all 10 S/T mutated to Ala (STIM1-10A). Here, we generate mouse embryonic fibroblasts (MEF) the STIM1-10A mouse line and a control MEF line (WT) that express wild-type STIM1 from a congenic mouse strain. These lines offer a unique model to address the role of STIM1 phosphorylation at endogenous expression and modulation levels in contrast to previous studies that relied mostly on overexpression. We show that STIM1 phosphorylation at ERK/CDK sites is not required for SOCE activation, cell migration, or ER partitioning during mitosis. These results rule out STIM1 phosphorylation as a regulator of SOCE, migration and ER distribution in mitosis.

Subcongenic Analysis of Quantitative Trait Loci Conferring Obesity and Hypercholesterolemia on Mouse Chromosome 1

Objectives The TALLYHO (TH) mouse is a polygenic model for obesity, type 2 diabetes and hyperlipidemia. We previously established a congenic mouse strain with TH donor segment on chromosome (Chr) 1 in a C57BL/6 J (B6) background that harbors quantitative trait loci (QTL) conferring obesity and hypercholesterolemia (The B6.TH-Chr1–128Mb). The congenic mouse developed increased adiposity and hypercholesterolemia and demonstrated that distal segment of Chr 1 from TH genome is necessary to cause both phenotypes. With the goal to identify the underlying genes regulating body fat and plasma cholesterol levels on mouse Chr 1, in this study we generated and characterized subcongenic lines with smaller TH donor segments. Methods Using the original B6.TH-Chr1–128Mb congenic mouse, we fixed three overlapping subcongenic lines over the distal region of Chr 1; one containing the full distal region of TH donor genome (39Mb in size) (B6.TH-Chr1–39Mb) and two nested overlapping lines (B6.TH-Chr1–30Mb and B6.TH-Chr1–20Mb). For mapping, all three lines of subcongenic mice and control B6 mice were weaned onto either chow or high fat (HF) diets at 4 weeks of age, and maintained on the respective diets. At 14 weeks of age, body composition including fat and lean mass was measured using EchoMRI-100 whole body composition analyzer, and plasma total cholesterol levels were determined using colorimetric assays. Data were analyzed by ANOVA using GraphPad Prism 8. Results On chow, body fat mass was not significantly different among all subcongenic mice and B6 mice. On HF diets, on the other hand, all three subcongenic lines of mice had significantly larger fat mass than B6 mice without genotype differences. These results suggest that the obesity candidate region is most likely located within the unique segment retained in B6.TH-Chr1–20Mb mice, delimited from the markers D1Mit105 and D1Mit361. Plasma total cholesterol levels were also significantly higher in B6.TH-Chr1–20Mb mice than them in B6 mice both on chow and HF diets. Conclusions We have created subcongenic lines, with smaller TH donor segments from the Chr 1 congenic interval, which develop detectable phenotypes, thus narrowing target intervals for positional cloning. Funding Sources This work was supported, in part, AHA 18AIREA33960437, NIH 1 R15 DK113604–01A1.