Phosphodiesterase 1A modulates cystogenesis in zebrafish

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Elevated cyclic adenosine monophosphate (cAMP) is implicated in polycystic kidney disease (PKD) pathogenesis.
• Phosphodiesterases (PDEs) regulate cAMP levels, and PDE1A is unique in its calcium/calmodulin activation, a condition altered in PKD cells.

Purpose of the Study:

• To investigate the role of the PDE1A subfamily in renal cyst formation using a zebrafish model.
• To determine if PDE1A is a potential therapeutic target for PKD.

Main Methods:

• Identified and characterized PDE1A splice isoforms in zebrafish.
• Utilized morpholinos to deplete PDE1A expression in zebrafish embryos.
• Assessed the effects of PDE1A depletion on pronephric cyst formation and other developmental phenotypes.
• Investigated the rescue effects of human PDE1A RNA and protein kinase A (PKA) inhibitors.
• Examined the interaction between PDE1A and polycystin-2 (PKD2) in a PKD zebrafish model.

Main Results:

• Two zebrafish PDE1A isoforms, analogous to human PDE1A1 and PDE1A4, were identified and shown to hydrolyze cAMP in a calcium/calmodulin-dependent manner.
• PDE1A depletion in zebrafish embryos led to the development of pronephric cysts, hydrocephalus, and body curvature.
• Administration of human PDE1A RNA and PKA inhibitors partially rescued these phenotypes.
• PDE1A depletion exacerbated phenotypes in pkd2 morphants, and human PDE1A RNA partially rescued these aggravated phenotypes.

Conclusions:

• PDE1A and cAMP signaling are integral to renal development and cystogenesis.
• PDE1A activity appears to be regulated downstream of polycystin-2.
• PDE1A represents a promising drug target for the treatment of PKD.