Evolution of higher mesenchymal CD44 expression in the human lineage

Abstract

CD44 is an extracellular matrix receptor implicated in cancer progression. CD44 increases the invasibility of skin (SF) and endometrial stromal fibroblasts (ESF) by cancer and trophoblast cells. We reasoned that the evolution of CD44 expression can affect both, the fetal–maternal interaction through CD44 in ESF as well as vulnerability to malignant cancer through expression in SF. We studied the evolution of CD44 expression in mammalian SF and ESF and demonstrate that in the human lineage evolved higher CD44 expression. Isoform expression in cattle and human is very similar suggesting that differences in invasibility are not due to the nature of expressed isoforms. We then asked whether the concerted gene expression increase in both cell types is due to shared regulatory mechanisms or due to cell type-specific factors. Reporter gene experiments with cells and cis-regulatory elements from human and cattle show that the difference of CD44 expression is due to cis effects as well as cell type-specific trans effects. These results suggest that the concerted expression increase is likely due to selection acting on both cell types because the evolutionary change in cell type-specific factors requires selection on cell type-specific functions. This scenario implies that the malignancy enhancing effects of elevated CD44 expression in humans likely evolved as a side-effect of positive selection on a yet unidentified other function of CD44. A possible candidate is the anti-fibrotic effect of CD44 but there are no reliable data showing that humans and primates are less fibrotic than other mammals.

Experimental and phylogenetic evidence for correlated gene expression evolution in endometrial and skin fibroblasts

“…One example is the evolution of the CD44 gene which is expressed in much higher levels in humans and the rhesus monkey than in other eutherian species tested. 21 CD44 is a hyaluronic acid receptor and its expression in the tumor stroma has been implicated in cancer malignancy. 30 , 31 Similarly, we have shown that GATA2 is a pro-invasibility transcription factor, meaning that a knockout of GATA2 in human SFs and ESFs leads to lower invasibility by both trophoblast as well as cancer cells.…”

“…Isolation of endometrial stromal fibroblasts: Cow ( Bos taurus ), dog ( Canis lupus ), cat ( Felis catus ), guinea pig ( Cavia porcellus ), horse ( Equus caballus ), rabbit ( Oryctolagus cuniculus ), sheep ( Ovis aries ), rat ( Rattus norvegicus ), SCID-CTRL and SCID-EVOL ESFs were obtained from fresh uterus samples. 21 2–3 mm uterus fragments were created using a scalpel and digested with 0.25% Trypsin–EDTA for 35 min at 37°C, followed by dissociation buffer (1 mg/ml collagenase, 1 mg/ml Dispase, 400 μg/mL DNase I) for 45 min at 37°C. Cell clumps were homogenized by passage through a 22-gauge syringe.…”

“…For this, we take advantage of transcriptomic data from cultured SFs and ESFs from 9 mammalian species described previously. 20 , 21 , 22 To test for correlated gene expression evolution, we use phylogenetic independent contrasts (PICs). 23 PICs estimate the amount of evolutionary change along independent parts of the phylogenetic tree.…”

Cell type and cell signaling innovations underlying mammalian pregnancy

“…Maximum parsimony was calculated using the castor package (v1.8.0) 29 . For continuous ancestral state reconstruction, restricted maximum likelihood was used via the ape package (v5.8) 30 as in 31 .…”

Monodelphis domestica Induced Pluripotent Stem Cells Reveal Metatherian Pluripotency Architecture

“…As mentioned in the results section, we used neoSF and monoiPSC RNASeq data generated in this study, as well as publicly available M. domestica single-cell RNASeq and bulk RNASeq data from previously published studies [ 19 , 28 , 42 ], for a comparative analysis to better understand marsupial pluripotency architecture. The published raw fastq files used in this study are described in Supplementary Table S4 and were downloaded from the NIH Sequence Read Archive (SRA).…”