Takayuki Ishige1, Sakae Itoga1, Emi Utsuno2, Motoi Nishimura1,2, Masaharu Yoshikawa3, Naoya Kato3, Kazuyuki Matsushita1,2, Osamu Yokosuka3, Fumio Nomura2.
Abstract
BACKGROUND: A genetic diagnosis has been rarely performed in benign familial hyperphosphatasaemia, and molecular mechanism largely remains unclear.
OBJECTIVES: We encountered a case with benign familial hyperphosphatasaemia of intestinal alkaline phosphatase (IAP). To elucidate the molecular mechanism, we performed ALPI gene sequencing and in vitro protein expression analysis.
METHODS: ALPI gene was sequenced by long-range PCR and massively parallel sequencing. The soluble and membrane-bound ALP activities of the cultured cell line, transfected with the wild-type or variant-type ALPI gene were analysed by a glycosylphosphatidylinositol (GPI)-cleaving assay.
RESULTS: We identified a deletion-insertion variant in the C-terminal end of the ALPI gene. This variant causes the attenuation of the hydrophobicity in GPI-anchor signal of IAP. An in vitro GPI-cleaving assay demonstrated that the membrane-bound IAP was greatly decreased, whereas the soluble IAP was increased, in the variant IAP.
CONCLUSIONS: The C-terminal variant in ALPI causes the benign familial hyperphosphatasaemia of IAP by the attenuation of the membrane-binding capability. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
BACKGROUND: A genetic diagnosis has been rarely performed in benign familial hyperphosphatasaemia, and molecular mechanism largely remains unclear.
OBJECTIVES: We encountered a case with benign familial hyperphosphatasaemia of intestinal alkaline phosphatase (IAP). To elucidate the molecular mechanism, we performed ALPI gene sequencing and in vitro protein expression analysis.
METHODS: ALPI gene was sequenced by long-range PCR and massively parallel sequencing. The soluble and membrane-bound ALP activities of the cultured cell line, transfected with the wild-type or variant-type ALPI gene were analysed by a glycosylphosphatidylinositol (GPI)-cleaving assay.
RESULTS: We identified a deletion-insertion variant in the C-terminal end of the ALPI gene. This variant causes the attenuation of the hydrophobicity in GPI-anchor signal of IAP. An in vitro GPI-cleaving assay demonstrated that the membrane-bound IAP was greatly decreased, whereas the soluble IAP was increased, in the variant IAP.
CONCLUSIONS: The C-terminal variant in ALPI causes the benign familial hyperphosphatasaemia of IAP by the attenuation of the membrane-binding capability. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
Entities:
Keywords:
diagnosis; gastroenterology; molecular genetics
Year: 2018
PMID： 29331981 DOI： 10.1136/jmedgenet-2017-104964
Source DB: PubMed Journal: J Med Genet ISSN： 0022-2593 Impact factor: 6.318