Human loss-of-function variants in the serotonin 2C receptor associated with obesity and maladaptive behavior

nature medicine Article https://doi.org/10.1038/s41591-022-02106-5 Human loss-of-function variants in the serotonin 2C receptor associated with obesity and maladaptive behavior Received: 26 October 2021 Accepted: 25 October 2022 Published online: 19 December 2022 Check for updates Yang He1,6, Bas Brouwers 2,6, Hesong Liu1,6, Hailan Liu1, Katherine Lawler2, Edson Mendes de Oliveira 2, Dong-Kee Lee3, Yongjie Yang1, Aaron R. Cox 4, Julia M. Keogh2, Elana Henning2, Rebecca Bounds2, Aliki Perdikari2, Vikram Ayinampudi2, Chunmei Wang1, Meng Yu1, Longlong Tu1, Nan Zhang1, Na Yin1, Junying Han1, Nikolas A. Scarcelli1, Zili Yan1, Kristine M. Conde 1, Camille Potts1, Jonathan C. Bean 1, Mengjie Wang1, Sean M. Hartig 3,4, Lan Liao3, Jianming Xu 3, Inês Barroso 5, Jacek Mokrosinski2, Yong Xu 1,3 & I. Sadaf Farooqi 2 Serotonin reuptake inhibitors and receptor agonists are used to treat obesity, anxiety and depression. Here we studied the role of the serotonin 2C receptor (5-HT2CR) in weight regulation and behavior. Using exome sequencing of 2,548 people with severe obesity and 1,117 control individuals without obesity, we identified 13 rare variants in the gene encoding 5-HT2CR (HTR2C) in 19 unrelated people (3 males and 16 females). Eleven variants caused a loss of function in HEK293 cells. All people who carried variants had hyperphagia and some degree of maladaptive behavior. Knock-in male mice harboring a human loss-of-function HTR2C variant developed obesity and reduced social exploratory behavior; female mice heterozygous for the same variant showed similar deficits with reduced severity. Using the 5-HT2CR agonist lorcaserin, we found that depolarization of appetite-suppressing proopiomelanocortin neurons was impaired in knock-in mice. In conclusion, we demonstrate that 5-HT2CR is involved in the regulation of human appetite, weight and behavior. Our findings suggest that melanocortin receptor agonists might be effective in treating severe obesity in individuals carrying HTR2C variants. We suggest that HTR2C should be included in diagnostic gene panels for severe childhood-onset obesity. Drugs that alter levels of the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) are widely prescribed for the treatment of obesity and neuropsychiatric disorders; however, they often exert adverse effects due to a lack of receptor specificity1 as 5-HT signals through at least 14 different receptors to regulate body weight, mood and behavior2,3. For example, second-generation antipsychotic drugs (clozapine and olanzapine) are highly effective at reducing psychotic symptoms, but cause increased hunger and weight gain in up to 60% 1 USDA/ARS Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA. 2University of Cambridge Metabolic Research Laboratories and NIHR Cambridge Biomedical Research Centre, Wellcome-MRC Institute of Metabolic Science, Addenbrooke’s Hospital, Cambridge, UK. 3Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA. 4Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Baylor College of Medicine, Houston, TX, USA. 5Exeter Centre of Excellence for Diabetes Research (EXCEED), University of Exeter Medical School, Exeter, UK. 6These authors contributed equally: Yang He, Bas Brouwers, Hesong Liu. e-mail: ; Nature Medicine | Volume 28 | December 2022 | 2537–2546 2537 Article https://doi.org/10.1038/s41591-022-02106-5 a 1 NH2 - M V N L R N A V ECL1 118 Y VWP L V 199 K E E F VN N T T C V L N 210 338 ECL3 E K S C D P D D C N Cell N P L Y Y R L R V L K Q A I C L I G V F L S M L membrane L L V P P V I L N I K E I L S I W P I S G I T L L I V 351 N 328 F 220 F 187 V 108 P 132 S V I I V M D L S P F F V F A I V V C V L F L M L G W W G I T V F I P M I I L S S L I G G M T I T L Y G V A D S A W A M I V F I N A I M I I V I V F F S C 73 L V S L L H I A Y T I V I G M I M C K C G N 314 364 146 235 174 93 V A F L I A I M T L V L L P M S N Y L S K A Y I S K Y V E T D T V A T A R R L K L N Y S R R F K H A V Q R N E K N Y F Y R I L A I N N M A K R S L 84 L L L MQ 158 R N R I H H ICL1 P N 374 A C 385 250 166 I S R E N F G Y H ICL2 T 299 K T G V E 260 R E P E P L S L G P K D 270 R K F L K CC K R N ICL3 R P T E C-term P N A S N E E E A K V 280 P N Q D Q N A R R R K K R 395 Q 290 I P 435 425 415 405 R V QME I G P E N D S A K E I V P E N T H R Y I N V N L E R G S L A T A A V E N L E L P V N P S S V V S E R I S S V -COOH 439 449 458 P W 59 S L 30 ECL2 N-term N Weight (kg) K HTR2C A171V mutation carrier 35 31 41 H 9 G D S T N F I D T V I A A V P S V S I D C QW V L L G I L H V L F S R G 21 F 25 20 15 A 10 5 0 0 1 2 3 4 5 6 Age of females (years) 40 HTR2C C266R mutation carrier 35 30 Weight (kg) F P D 51 G V Q b 40 25 20 15 10 5 0 0 1 2 3 4 5 6 Age of females (years) Fig. 1 | Rare variants affecting 5-HT2CR identified in people with severe obesity. a, Rare variants identified in individuals with severe early-onset obesity shown on a schematic of the 5-HT2CR protein; ECL and ICL refer to extra- and intracellular loops of the G-protein-coupled receptor (GPCR), respectively; C-term, C-terminal domain of the protein. b, Weight charts of two female probands (5th and 95th percentiles based on reference data for the UK population shown as dashed lines). of patients, which represents a major barrier to their long-term use4. Understanding the mechanisms by which serotonin’s effects on food intake, body weight, mood and behavior are mediated in humans could inform the development of more targeted therapies for a range of clinical disorders. Studies in mice have shown that the appetite-suppressing actions of 5-HT are largely mediated by 5-HT 2CRs expressed on hypothalamic proopiomelanocortin (POMC) neurons5–7, which play a major role in weight regulation. A complete lack of POMC due to bi-allelic loss-of-function mutations causes hyperphagia and severe childhood-onset obesity8. This genetic obesity syndrome and other closely related disorders of the leptin–melanocortin pathway are treatable by setmelanotide, a melanocortin 4 receptor (MC4R) agonist, which has been licensed for clinical use in the UK, Europe and the US9–11. Here, we set out to investigate the potential contribution of 5-HT2CR signaling to human weight regulation and the interaction between 5-HT2CRs and the melanocortin pathway. lies on the X chromosome in humans; 16 girls carried a heterozygous variant and 3 boys carried a hemizygous variant (variant on their only X chromosome). Three families of probands carrying variants that were not found in controls, consented to co-segregation studies. The four people carrying rare HTR2C variants in these families had overweight or obesity (Table 1). Results Rare variants in HTR2C in people with severe obesity We analyzed exome sequencing and targeted resequencing on 2,548 (46% male and 54% female) European ancestry individuals with s (...truncated)