A Comparative Genomic and Phylogenetic Analysis of the Origin and Evolution of the CCN Gene Family.

CCN gene family members have recently been identified as multifunctional regulators involved in diverse biological functions, especially in vascular and skeletal development. In the present study, a comparative genomic and phylogenetic analysis was performed to show the similarities and differences in structure and function of CCNs from different organisms and to reveal their potential evolutionary relationship. First, CCN homologs of metazoans from different species were identified. Then we made multiple sequence alignments, MEME analysis, and functional sites prediction, which show the highly conserved structural features among CCN metazoans. The phylogenetic tree was further established, and thus CCNs were found undergoing extensive lineage-specific duplication events and lineage-specific expansion during the evolutionary process. Besides, comparative analysis about the genomic organization and chromosomal CCN gene surrounding indicated a clear orthologous relationship among these species counterparts. At last, based on these research results above, a potential evolutionary scenario was generated to overview the origin and evolution of the CCN gene family.

Eyeing the Cyr61/CTGF/NOV (CCN) group of genes in development and diseases: highlights of their structural likenesses and functional dissimilarities.

"CCN" is an acronym referring to the first letter of each of the first three members of this original group of mammalian functionally and phylogenetically distinct extracellular matrix (ECM) proteins [i.e., cysteine-rich 61 (CYR61), connective tissue growth factor (CTGF), and nephroblastoma-overexpressed (NOV)]. Although "CCN" genes are unlikely to have arisen from a common ancestral gene, their encoded proteins share multimodular structures in which most cysteine residues are strictly conserved in their positions within several structural motifs. The CCN genes can be subdivided into members developmentally indispensable for embryonic viability (e.g., CCN1, 2 and 5), each assuming unique tissue-specific functions, and members not essential for embryonic development (e.g., CCN3, 4 and 6), probably due to a balance of functional redundancy and specialization during evolution. The temporo-spatial regulation of the CCN genes and the structural information contained within the sequences of their encoded proteins reflect diversity in their context and tissue-specific functions. Genetic association studies and experimental anomalies, replicated in various animal models, have shown that altered CCN gene structure or expression is associated with "injury" stimuli--whether mechanical (e.g., trauma, shear stress) or chemical (e.g., ischemia, hyperglycemia, hyperlipidemia, inflammation). Consequently, increased organ-specific susceptibility to structural damages ensues. These data underscore the critical functions of CCN proteins in the dynamics of tissue repair and regeneration and in the compensatory responses preceding organ failure. A better understanding of the regulation and mode of action of each CCN member will be useful in developing specific gain- or loss-of-function strategies for therapeutic purposes.