Expression Profile and Implications of ACE2; The Receptor for New SARS-CoV-2

Expansion of novel coronavirus disease 2019 (COVID-19) involves various risk factors including clinical, genetic, demographic and environmental manifestation but they are insufficient to explain disease pathogenesis. With patients ranging from completely asymptomatic to many suffering mild to severe illness, indicates that COVID- 19 should better be studied at genetic level as different genetic backgrounds predispose to variability in infection susceptibility. Recently, it is recognized that severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) binds and internalized by the host cells through cell surface receptors angiotensin-converting enzyme 2 (ACE2), which is expressed significantly in variety of human tissues particularly in the lower and upper respiratory tract. To scrutinize the expression profiles and clinical implications of ACE2 gene in humans, literature was extensively reviewed. In common, various studies reported that ACE2 receptor protein is highly conserved among different species, the expression pattern is tissue specific mainly observed in cardiovascular system, breast cells, testis, adipose tissue, kidney, lymphocytes and gastrointestinal system other than the upper and lower respiratory tract. This significant expression makes these organs vulnerable to SARS-CoV-2 virus and hence many comorbidities may be observed during the course of infection. The present review on expression profile of ACE2 not only proposes potential clues for COVID-19 pathogenesis but also designate clinical values of ACE2 gene in heterogeneous disorders.