Objective: In an ongoing effort to identify the genetic variation that contributes to obesity in American Indians, known Bardet-Biedl syndrome (BBS) genes were analyzed for an effect on BMI and leptin signaling.
Methods: Potentially deleterious variants (Combined Annotation Dependent Depletion score > 20) in BBS genes were identified in whole-exome sequence data from 6,851 American Indians informative for BMI. Common variants (detected in ≥ 10 individuals) were analyzed for association with BMI; rare variants (detected in < 10 individuals) were analyzed for mean BMI of carriers. Functional assessment of variants' effect on signal transducer and activator of transcription 3 (STAT3) activity was performed in vitro.
Results: One common variant, rs59252892 (Thr549Ile) in BBS9, was associated with BMI (P = 0.0008, β = 25% increase per risk allele). Among rare variants for which carriers had severe obesity (mean BMI > 40 kg/m2 ), four were in BBS9. In vitro analysis of BBS9 found the Ile allele at Thr549Ile had a 20% increase in STAT3 activity compared with the Thr allele (P = 0.01). Western blot analysis showed the Ile allele had a 15% increase in STAT3 phosphorylation (P = 0.006). Comparable functional results were observed with Ser545Gly and Val209Leu but not Leu665Phe and Lys810Glu.
Conclusions: Potentially functional variants in BBS genes in American Indians are reported. However, functional evidence supporting a causal role for BBS9 in obesity is inconclusive.
© 2021 Regeneron Pharmaceuticals Inc. Obesity published by Wiley Periodicals LLC on behalf of The Obesity Society. This article has been contributed to by US Government employees and their work is in the public domain in the USA.