9049

AIP

ARA9|FKBP16|FKBP37|SMTPHN|XAP-2|XAP2;aryl hydrocarbon receptor interacting protein;AIP;aryl hydrocarbon receptor interacting protein

AH receptor-interacting protein|HBV X-associated protein 2|HBV-X associated protein|aryl hydrocarbon receptor-interacting protein|aryl-hydrocarbon receptor interacting protein|aryl-hydrocarbon receptor-interacting protein|immunophilin homolog ARA9

11q13.3

protein-coding

BACKGROUND: Germline aryl hydrocarbon receptor-interacting protein (AIP) mutations occur in 15% of familial isolated pituitary adenoma (FIPA) cases. To date, studies have focused on the identification of such mutations in large international cohorts. Detailed genetic and clinical studies within AIP mutation-positive families have been limited. Aim: To undertake a comprehensive study of a large Brazilian FIPA kindred with an E174 frameshift (E174fs) AIP mutation to assess clinical, hormonal, and radiological features in mutation carriers. METHODS: The kindred included 122 subjects across six generations; allunderwent clinical examination. Genetic studies were performed to identify E174fs mutation carriers. E174fs-positive subjects underwent magnetic resonance imaging(MRI) and hormonal assessments. RESULTS: Of the ten germline AIP mutation carriers, three had pituitary tumors, while seven were asymptomatic carriers. Three patients with pituitary tumors showed variability in terms of tumor phenotype (two with acromegaly, one with prolactinoma, or mixed prolactin/GH-secreting tumor) and age at diagnosis; both patients with acromegaly had poor responses to octreotide. tumor AIP immunohistochemistry from the operated patient showed decreased expression when compared with normal tissue. Two adult subjects with normal MRI had elevated IGF-I in the absence of other causes. A 2-year-old child with the E174fs mutation and a normal MRI had premature thelarche, ovarian development, and advanced bone age in the absence of other underlying causes. CONCLUSIONS: The penetrance of pituitary tumors in AIP mutation-positive adult subjects was 33.3%, while clinical/hormonal features were variable. The features noted in AIP-mutation carriers in this kindred suggest that clinical characteristics of such carriers may extend beyond pituitary tumors.

Prolactinomas are rare tumors in prepubertal children. A prolactinoma in a youngchild may be due to sequence variants in genes that are known to cause these tumors ( MEN1, PRKAR1A, AIP). An 11-year-old boy with a macroprolactinoma was treated with cabergoline and the tumor receded. We studied the patient and his family for genetic causes of this tumor. No mutations were present in the codingsequence of PRKAR1A and AIP. A novel heterozygous substitution (IVS3-7 c>a) was identified in intron 3 of MEN1. We also found an additional PCR amplicon that incorporated the entire intron 3 of the gene (210 bp) in the patient's cDNA. Thesame amplicon was present with lower intensity in some of the control individuals who were not mutation carriers. Intron 3 harbors an in-frame stop codon and its incorporation is predicted to result in a prematurely terminated protein. We conclude that a novel MEN1 variation was identified in a young boy with prolactinoma and six of his relatives who did not present with prolactinoma or other MEN1 related symptoms. This novel MEN1 variation may be associated with low penetrance of the disease. The IVS3-7 c>a defect is suggested to be pathogenic because it is associated with lower menin levels in the cells of these patients,but its consequences may be mitigated by a variety of factors including changes in transcription and translation of the MEN1 gene.#CI- Copyright Georg Thieme Verlag KG Stuttgart. New York.