Primary cilia are organelles that are present on many different cell types, either transiently or permanently. They play a crucial role in receiving signals from the environment and passing these signals to other parts of the cell. In that way, they are involved in diverse processes such as adipocyte differentiation and olfactory sensation. Mutations in genes coding for ciliary proteins often have pleiotropic effects and lead to clinical conditions, ciliopathies, with multiple symptoms. In this study, we reviewed observations from ciliopathies with obesity as one of the symptoms. It shows that variation in cilia-related genes is itself not a major cause of obesity in the population but may be a part of the multifactorial aetiology of this complex condition. Both common polymorphisms and rare deleterious variants may contribute to the obesity risk. Genotype-phenotype relationships have been noticed. Among the ciliary genes, obesity differs with regard to severity and age of onset, which may relate to the influence of each gene on the balance between pro- and anti-adipogenic processes. Analysis of the function and location of the proteins encoded by these ciliary genes suggests that obesity is more linked to activities at the basal area of the cilium, including initiation of the intraflagellar transport, but less to the intraflagellar transport itself. Regarding the role of cilia, three possible mechanistic processes underlying obesity are described: adipogenesis, neuronal food intake regulation and food odour perception.
Keywords: 5)-diphosphate; 5)P2 phosphatidylinositol (4; ADCY3 adenylate cyclase 3; ALMS1 Alström syndrome protein 1; ANKRD26 ankyrin repeat domain 26; ARL6 ADP-ribosylation factor-like 6; AURKA aurora kinase A; Adipocyte differentiation; BBS Bardet–Biedl syndrome; BTC basal transport complex; CCT chaperonin containing TCP1; Food intake regulation; Food odour sensation; HDAC6 histone deacetylase 6; IFT intraflagellar transport; IGF1-R insulin-like growth factor 1 receptor; INPP5E inositol polyphosphate-5-phosphatase E; KIF3A kinesin family member 3A; NPHP nephronophthisis; OR olfactory receptor; Obesity; PCM1 pericentriolar material 1; PDE6D phosphodiesterase 6D; PI(4; POMC pro-opiomelanocortin; PTHB1 parathyroid hormone responsive B1; Primary cilia; RABL4 RAB-like 4; RPGRIP1L retinitis pigmentosa GTPase regulator interacting protein 1-like; SDCCAG8 serologically defined colon cancer antigen 8; SHH sonic hedgehog; TCTN1-3 tectonic family member 1–3.