Unexpected mosaicism of R201H-GNAS1 mutant-bearing cells in the testes underlie macro-orchidism without sexual precocity in McCune–Albright syndrome

• Published in: Human molecular genetics 2006-12, Vol.15 (24), p.3538-3543
• Main Authors: Rey, Rodolfo A., Venara, Marcela, Coutant, Régis, Trabut, Jean-Baptiste, Rouleau, Stéphanie, Lahlou, Najiba, Sultan, Charles, Limal, Jean-Marie, Picard, Jean-Yves, Lumbroso, Serge
• Format: Article
• Language: English
• Subjects: Base Sequence; Biological and medical sciences; Cell Line; Child; Child, Preschool; Chromogranins; Diseases of the osteoarticular system; Fibrous Dysplasia, Polyostotic - genetics; Fibrous Dysplasia, Polyostotic - physiopathology; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; GTP-Binding Protein alpha Subunits, Gs - genetics; GTP-Binding Protein alpha Subunits, Gs - physiology; Humans; Leydig Cells - metabolism; Leydig Cells - pathology; Luciferases - genetics; Luciferases - metabolism; Male; Malformations and congenital and or hereditary diseases involving bones. Joint deformations; Medical sciences; Models, Biological; Molecular and cellular biology; Mosaicism; Mutation; Promoter Regions, Genetic; Puberty, Precocious - genetics; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Sertoli Cells - metabolism; Sertoli Cells - pathology; Signal Transduction; Testis - metabolism; Testis - pathology; Transfection
• ISSN: 0964-6906; 1460-2083
• DOI: 10.1093/hmg/ddl430

McCune–Albright syndrome (MAS), usually presenting with polyostotic bone dysplasia, café-au-lait skin lesions and sexual precocity, results from a somatic activating mutation of the GNAS1 gene, which encodes the Gs-alpha protein involved in signalling of several G-protein-coupled receptors. The clinical spectrum depends on tissue distribution of mutant-bearing cells. Sexual precocity has been ascribed to the occurrence of a mutant GNAS1 allele in the gonadal anlage, from which all somatic cells of the differentiated gonads arise. In boys, precocious activation of Leydig cell androgen secretion results in pubertal spermatogenesis, leading to testicular enlargement, and in the development of secondary sex characteristics. However, sexual precocity is rare in MAS males while isolated testicular enlargement is frequently observed. We recently reported the case of a boy with macro-orchidism and signs of Sertoli cell hyperactivity but no signs of hyperandrogenism, which was unexpected since Gs-alpha is functional in both Sertoli and Leydig cells. To understand its pathophysiology, we microdissected an available testicular biopsy to separate Sertoli from Leydig cells. The R201H-GNAS1 allele was present only in Sertoli cells, resulting in isolated Sertoli cell hyperfunction, evidenced by increased AMH expression and cell hyperplasia leading to prepubertal macro-orchidism, with no signs of Leydig cell activation. The different early embryologic origin of precursors contributing to Sertoli and Leydig cell lineages may underlie the differential existence of the mutated GNAS1 gene. Lack of occurrence of the mutation in Leydig cells may explain why sexual precocity is rarely observed in boys with MAS.