Parp12, a member of the poly-ADP-ribosyl polymerase (PARPs) family, is a mon(ADP-ribosyl) transferase. It is involved in multiple biological processes such as protein translation, inflammation, and is a key regulator of mitochondrial function [3]. ADP-ribosylation, a process catalyzed by Parp12, is an important aspect of the innate immune response [4]. Gene knockout mouse models have been crucial in understanding Parp12's functions.

In mouse oocytes, Parp12 depletion leads to abnormal spindle organization, chromosome misalignment, increased aneuploidy, and activation of the spindle assembly checkpoint, indicating its essential role in oocyte meiotic maturation [1]. In thermogenic adipocytes, knockdown of Parp12 reduces UCP1 expression and mitochondrial respiration, highlighting its significance in maintaining mitochondrial function [2]. In a study on coronavirus, Parp12 -/- mice showed increased replication of a Mac1 mutant coronavirus in bone-marrow-derived macrophages and mice, demonstrating its role in repressing virus replication [4]. In hepatocellular carcinoma, Parp12 deficiency promotes cell migration, invasion, and metastasis by regulating FHL2 stability and TGF-β1 expression [5].

In conclusion, Parp12 is essential for oocyte meiotic maturation, mitochondrial function in adipocytes, antiviral response against certain coronaviruses, and acts as a tumor suppressor in hepatocellular carcinoma. The use of Parp12 knockout mouse models has significantly enhanced our understanding of its role in these biological processes and disease conditions.