{"title":"Variants in both the N- or C-terminal domains of IHH lead to defective secretion causing short stature and skeletal defects.","authors":"Francisca Díaz-González, Lucía Sentchordi-Montané, Elsa Lucas-Castro, Silvia Modamio-Høybjør, Karen E Heath","doi":"10.1093/ejendo/lvae072","DOIUrl":null,"url":null,"abstract":"<p><strong>Background: </strong>Heterozygous Indian Hedgehog gene (IHH) variants are associated with brachydactyly type A1 (BDA1). However, in recent years, numerous variants have been identified in patients with short stature and more variable forms of brachydactyly. Many are located in the C-terminal domain of IHH (IHH-C), which lacks signaling activity but is critical for auto-cleavage and activation of the N-terminal (IHH-N) peptide. The absence of functional studies of IHH variants, particularly for those located in IHH-C, has led to these variants being classified as variants of uncertain significance (VUS).</p><p><strong>Objective: </strong>To establish a simple functional assay to determine the pathogenicity of IHH VUS and confirm that variants in the C-terminal domain affect protein function.</p><p><strong>Design/methods: </strong>In vitro studies were performed for 9 IHH heterozygous variants, to test their effect on secretion and IHH intracellular processing by western blot of cells expressing each variant.</p><p><strong>Results: </strong>IHH secretion was significantly reduced in all mutants, regardless of the location. Similarly, intracellular levels of N-terminal and C-terminal IHH peptides were severely reduced in comparison with the control. Two variants present at a relatively high frequency in the general population also reduced secretion but to a lesser degree in the heterozygous state.</p><p><strong>Conclusions: </strong>These studies provide the first evidence that variants in the C-terminal domain affect the secretion capacity of IHH and thus, reduce availability of IHH ligand, resulting in short stature and mild skeletal defects. The secretion assay permits a relatively easy test to determine the pathogenicity of IHH variants. All studied variants affected secretion and interestingly, more frequent population variants appear to have a deleterious effect and thus contribute to height variation.</p>","PeriodicalId":11884,"journal":{"name":"European Journal of Endocrinology","volume":null,"pages":null},"PeriodicalIF":5.3000,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Endocrinology","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1093/ejendo/lvae072","RegionNum":1,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENDOCRINOLOGY & METABOLISM","Score":null,"Total":0}
引用次数: 0
Abstract
Background: Heterozygous Indian Hedgehog gene (IHH) variants are associated with brachydactyly type A1 (BDA1). However, in recent years, numerous variants have been identified in patients with short stature and more variable forms of brachydactyly. Many are located in the C-terminal domain of IHH (IHH-C), which lacks signaling activity but is critical for auto-cleavage and activation of the N-terminal (IHH-N) peptide. The absence of functional studies of IHH variants, particularly for those located in IHH-C, has led to these variants being classified as variants of uncertain significance (VUS).
Objective: To establish a simple functional assay to determine the pathogenicity of IHH VUS and confirm that variants in the C-terminal domain affect protein function.
Design/methods: In vitro studies were performed for 9 IHH heterozygous variants, to test their effect on secretion and IHH intracellular processing by western blot of cells expressing each variant.
Results: IHH secretion was significantly reduced in all mutants, regardless of the location. Similarly, intracellular levels of N-terminal and C-terminal IHH peptides were severely reduced in comparison with the control. Two variants present at a relatively high frequency in the general population also reduced secretion but to a lesser degree in the heterozygous state.
Conclusions: These studies provide the first evidence that variants in the C-terminal domain affect the secretion capacity of IHH and thus, reduce availability of IHH ligand, resulting in short stature and mild skeletal defects. The secretion assay permits a relatively easy test to determine the pathogenicity of IHH variants. All studied variants affected secretion and interestingly, more frequent population variants appear to have a deleterious effect and thus contribute to height variation.
期刊介绍:
European Journal of Endocrinology is the official journal of the European Society of Endocrinology. Its predecessor journal is Acta Endocrinologica.
The journal publishes high-quality original clinical and translational research papers and reviews in paediatric and adult endocrinology, as well as clinical practice guidelines, position statements and debates. Case reports will only be considered if they represent exceptional insights or advances in clinical endocrinology.
Topics covered include, but are not limited to, Adrenal and Steroid, Bone and Mineral Metabolism, Hormones and Cancer, Pituitary and Hypothalamus, Thyroid and Reproduction. In the field of Diabetes, Obesity and Metabolism we welcome manuscripts addressing endocrine mechanisms of disease and its complications, management of obesity/diabetes in the context of other endocrine conditions, or aspects of complex disease management. Reports may encompass natural history studies, mechanistic studies, or clinical trials.
Equal consideration is given to all manuscripts in English from any country.