Differential Expression of α, β, and γ Protocadherin Isoforms During Differentiation, Aging, and Cancer

The cadherin family of cell surface glycoproteins plays a fundamental role in cell-cell recognition, thereby participating in diverse biological process such as embryonic morphogenesis and oncogenic transformation. The subset of clustered protocadherin (PCDH) genes generated from the α, β, and γ loci, have been widely studied for their potential role in neuronal cell-cell recognition and neurogenesis, however their broader role in normal embryonic development and cancer has not been examined in detail. We utilized human embryonic stem (hES) cells to model early human development in vitro , comparing PCDH isoform transcription in diverse types of embryonic progenitors with normal adult-derived and cancer counterparts. Embryonic progenitors express genes from the α and β cluster at levels comparable to that seen in the CNS, while fetal and adult-derived cells express primarily from the γ cluster. Replicative senescence left fibroblasts with markedly lower expression of all isoforms. We observe that an embryonic pattern of clustered protocadherin gene expression and associated CpG island methylation is commonly associated with cancer cell lines from diverse tissue types. The differential regulation of the α, β, and γ loci coincide with alternate regions of DNA accessibility at CTCF binding sites and lamina-associated domains and CPL expression correlated with the expression of LMNA and LMNB1 . These observations support a potential role for the differential regulation of genes within the clustered protocadherin locus in selective cell-cell adhesion during embryogenesis, regeneration, cancer and aging. ### Competing Interest Statement HS, IL, JL, PS, JJ, DL and MDW are employees of and stockholders in AgeX, Inc., (Alameda, CA). KBC is an employee of Eclipse Innovations, (San Diego, CA) and a stockholder of AgeX, Inc.