WNT10B mutations in human obesity

Abstract

Aims/hypothesis: Recent studies suggest that wingless-type MMTV integration site family, member 10B (WNT10B) may play a role in the negative regulation of adipocyte differentiation in vitro and in vivo. In order to determine whether mutations in WNT10B contribute to human obesity, we screened two independent populations of obese subjects for mutations in this gene.

Subjects and methods: We studied 96 subjects with severe obesity of early onset (less than 10 years of age) from the UK Genetics of Obesity Study and 115 obese Italian subjects of European origin.

Results: One proband with early-onset obesity was found to be heterozygous for a C256Y mutation, which abrogated the ability of WNT10B to activate canonical WNT signalling and block adipogenesis and was not found in 600 control alleles. All relatives of the proband who carried this allele were either overweight or obese. Three other rare missense variants were found in obese probands, but these did not clearly cosegregate with obesity in family studies and one (P301S), which was found in three unrelated subjects with early-onset obesity, had normal functional properties.

Conclusions/interpretation: These mutations represent the first naturally occurring missense variants of WNT10B. While the pedigree analysis in the case of C256Y WNT10B does not provide definitive proof of a causal link of this variant with obesity, the finding of a non-functioning WNT10B allele in a human family affected by obesity should encourage further study of this gene in other obese populations.

Fig. 1

a Cysteine 256 is absolutely conserved among all WNT family members. b Family trees of all subjects with non-synonymous variants identified in group A (early-onset obesity) with BMI (BMI standard deviation scores for children) indicated. Probands are indicated by filled symbols. c Family trees of all subjects with non-synonymous variants identified in group B (obese Italian subjects) with BMI indicated. Probands are indicated by filled symbols. M variants on one allele, N normal genotype on one allele

Fig. 2

Functional properties of wild-type, C256Y and P301S WNT10B in cultured 3T3-L1 cells. a Western blot analysis of cytosolic β-catenin levels during differentiation of empty vector control (EV) and wild-type, C256Y and P301S WNT10B producing 3T3-L1 preadipocytes. 0 onset of differentiation (2 days after confluence); 4, 8, 4 and 8 days after induction of differentiation, respectively. Data are representative of three independent experiments. b Effect of wild-type, C256Y and P301S WNT10B on TOP-Flash reporter activity in 3T3-L1 cells. Results are expressed as fold difference relative to EV. All results are mean±SD of three independent experiments. ***p<0.001 for comparisons with EV. RLU relative luciferase units. c Effects of wild-type, C256Y and P301S WNT10B on differentiation of 3T3-L1 preadipocytes. Top Oil-Red O staining of 3T3-L1 cells 8 days after induction of differentiation. Bottom Light microscope images of cells stained with Oil Red O. d–g Expression of adipogenic markers and WNT10B as indicated in EV and wild-type, C256Y and P301S WNT10B-producing 3T3-L1 cells at onset (2 days after confluence, open bars) and 6 days (closed bars) after induction of differentiation. All data are mean±SD of three independent experiments