Genetic expansion of chaperonin ‐containing TCP‐1 (CCT/TRiC) complex subunits yields testis‐specific isoforms required for spermatogenesis in planarian flatworms

Chaperonin ‐containing Tail‐less complex polypeptide 1 (CCT) is a highly conserved, hetero‐oligomeric complex that ensures proper folding of actin, tubulin, and regulators of mitosis. Eight subunits (CCT1‐8) make up this complex, and every subunit has a homolog expressed in the testes and somatic tissu e of the planarian flatwormSchmidtea mediterranea. Gene duplications of four subunits in the genomes ofS. mediterranea and other planarian flatworms created paralogs to CCT1, CCT3, CCT4, and CCT8 that are expressed exclusively in the testes. Functional analyses revealed that each CCT subunit expressed in theS. mediterranea soma is essential for homeostatic integrity and survival, whereas sperm elongation defects were observed upon knockdown of each individual testis ‐specific paralog (Smed ‐cct1B;Smed ‐cct3B;Smed ‐cct4A; andSmed ‐cct8B), regardless of potential redundancy with paralogs expressed in both testes and soma (Smed ‐cct1A;Smed ‐cct3A;Smed ‐cct4B; andSmed ‐cct8A). Yet, no detriment was observed in the number of adult somatic stem cells (neoblasts) that maintain differentiated tissue in planarians. Thus, expression of all eight CCT subunits is required to execute the essential functions of the CCT complex. Furthermore, expression of the somatic paralogs in planarian testes is not sufficient to complete spermatogenesis when testis ‐specific paralogs are knocked down, suggesting that the evolution of chaperonin subunits may drive changes in the...
Source: Molecular Reproduction and Development - Category: Reproduction Medicine Authors: Tags: RESEARCH ARTICLE Source Type: research