title: Identification and functional characterization of natural human melanocortin 1 receptor mutant alleles in Pakistani population.
abstract: Melanocortin 1 receptor (MC1R), a Gs protein-coupled receptor of the melanocyte's plasma membrane, is a major determinant of skin pigmentation and phototype. Upon activation by α-melanocyte stimulating hormone, MC1R triggers the cAMP cascade to stimulate eumelanogenesis. We used whole-exome sequencing to identify causative alleles in Pakistani families with skin and hair hypopigmentation. Six MC1R mutations segregated with the phenotype in seven families, including a p.Val174del in-frame deletion and a p.Tyr298* nonsense mutation, that were analyzed for function in heterologous HEK293 cells. p.Tyr298* MC1R showed no agonist-induced signaling to the cAMP or ERK pathways, nor detectable agonist binding. Conversely, signaling was comparable for p.Val174del and wild-type in HEK cells overexpressing the proteins, but binding analysis suggested impaired cell surface expression. Flow cytometry and confocal imaging studies revealed reduced plasma membrane expression of p.Val174del and p.Tyr298*. Therefore, p.Tyr298* was a total loss-of-function (LOF) allele, while p.Val174del displayed a partial LOF attribute.
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Mohsin
authors.initials: M
authors.lastname: Shahzad
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and IMIB-Arrixaca, Murcia, Spain.
authors.forename: Julia
authors.initials: J
authors.lastname: Sires Campos
authors.affiliation: Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
authors.forename: Nabeela
authors.initials: N
authors.lastname: Tariq
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and IMIB-Arrixaca, Murcia, Spain.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Herraiz Serrano
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Rizwan
authors.initials: R
authors.lastname: Yousaf
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and IMIB-Arrixaca, Murcia, Spain.
authors.forename: Celia
authors.initials: C
authors.lastname: Jiménez-Cervantes
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.|Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
authors.forename: Sairah
authors.initials: S
authors.lastname: Yousaf
authors.affiliation: Molecular Biology & Genetics Department, Medical Research Center, Liaquat University of Medical & Health Sciences, Jamshoro, Pakistan.
authors.forename: Yar M
authors.initials: YM
authors.lastname: Waryah
authors.affiliation: Institute of Pharmaceutical Sciences, University of Veterinary & Animal Sciences, Lahore, Pakistan.
authors.forename: Haseeb A
authors.initials: HA
authors.lastname: Dad
authors.affiliation: Division of Medical Genetics, Department of Medicine, University of Washington, Seattle, WA, USA.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Blue
authors.affiliation: McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Nara
authors.initials: N
authors.lastname: Sobreira
authors.affiliation: Yale Center for Genome Analysis, Yale University, West Haven, CT, USA.
authors.forename: Francesc
authors.initials: F
authors.lastname: López-Giráldez
authors.affiliation: Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
authors.forename: Tasleem
authors.initials: T
authors.lastname: Kausar
authors.affiliation: Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Ali
authors.affiliation: Molecular Biology & Genetics Department, Medical Research Center, Liaquat University of Medical & Health Sciences, Jamshoro, Pakistan.
authors.forename: Ali M
authors.initials: AM
authors.lastname: Waryah
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Saima
authors.initials: S
authors.lastname: Riazuddin
authors.affiliation: Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
authors.forename: Rehan S
authors.initials: RS
authors.lastname: Shaikh
authors.affiliation: Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia and IMIB-Arrixaca, Murcia, Spain.
authors.forename: José C
authors.initials: JC
authors.lastname: García-Borrón
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.
authors.forename: Zubair M
authors.initials: ZM
authors.lastname: Ahmed
mesh_terms: D000483:Alleles; D005190:Family; D005260:Female; D006801:Humans; D017496:Hypopigmentation / Q000235:genetics; D008297:Male; D009154:Mutation / Q000235:genetics*; D010154:Pakistan; D010375:Pedigree; D010641:Phenotype; D044102:Receptor, Melanocortin, Type 1 / Q000235:genetics*
chemical_list: D044102:Receptor, Melanocortin, Type 1
keywords: cAMP signaling; hypopigmentation; melanocortin 1 receptor; melanocytes