Molecular changes in the membranes of mouse erythroid cells accompanying differentiation.

The development of the mouse erythroblast to a mature erythrocyte is accompanied by changes in the composition and properties of the plasma membranes of these cells. Using double fluorescence techniques, we have simultaneously determined the distribution of lectin receptors and spectrin on the membranes of these cells. The lateral mobility of the lectin receptors in the membranes decreases as differentiation proceeds, and this is accompanied by an increasing concentration of spectrin associated with the membranes. The most significant concentration of spectrin occurs, however, during the enucleation of the late erythroblast, where we observe a complete segregation of the spectrin to the incipient reticulocyte, as well as a previously observed enrichment of receptors for concanavalin A into the plasma membrane surrounding the extruding nucleus. On the basis of these and other observations, we explore the possible molecular mechanisms involved in erythroblast enucleation and the role of spectrin in the regulation of protein mobility in erythroid cell membranes.     

Genome-wide methylation and expression differences in HPV(+) and HPV(?) squamous cell carcinoma cell lines are consistent with divergent mechanisms of carcinogenesis

Oncogenic human papillomaviruses (HPV) are associated with nearly all cervical cancers and are increasingly important in the etiology of oropharyngeal tumors. HPV-associated head and neck squamous cell carcinomas (HNSCC) have distinct risk profiles and appreciate a prognostic advantage compared to HPV-negative HNSCC. Promoter hypermethylation is widely recognized as a mechanism in the progression of HNSCC, but the extent to which this mechanism is consistent between HPV(+) and HPV(−) tumors is unknown. To investigate the epigenetic regulation of gene expression in HPV-induced and carcinogen-induced cancers, we examined genome-wide DNA methylation and gene expression in HPV(+) and HPV(−) SCC cell lines. We used two platforms: the Illumina Infinium Methylation BeadArray and tiling arrays, and confirmed illustrative examples with pyrosequencing and quantitative PCR. These analyses indicate that HPV(+) cell lines have higher DNA methylation in genic and LINE-1 regions than HPV(−) cell lines. Differentially methylated loci between HPV(+) and HPV(−) cell lines significantly correlated with HPV-typed HNSCC primary tumor DNA methylation levels. Novel findings include higher promoter methylation of polycomb repressive complex 2 target genes in HPV(+) cells compared to HPV(−) cells and increased expression of DNMT3A in HPV(+) cells. Additionally, CDKN2A and KRT8 were identified as interaction hubs among genes with higher methylation and lower expression in HPV(−) cells. Conversely, RUNX2, IRS-1 and CCNA1 were major hubs with higher methylation and lower expression in HPV(+) cells. Distinct HPV(+) and HPV(−) epigenetic profiles should provide clues to novel targets for development of individualized therapeutic strategies.Key words: epigenetics, human papillomavirus, HNSCC, DNA methylation, squamous cell carcinoma, gene expression, microarrays, illumina infinium humanmethylation27 beadarray