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Further characterization of Borjeson-Forssman-Lehmann syndrome in females due to de novo variants in PHF6


Abstract

While inherited hemizygous variants in PHF6 cause X-linked recessive Borjeson-Forssman-Lehmann syndrome (BFLS) in males, de novo heterozygous variants in females are associated with an overlapping but distinct phenotype, including moderate to severe intellectual disability, characteristic facial dysmorphism, dental, finger and toe anomalies and linear skin pigmentation. By personal communication with colleagues, we assembled eleven additional females with BFLS due to variants in PHF6. We confirm the distinct phenotype to include variable intellectual disability, recognizable facial dysmorphism and other anomalies. We observed skewed X-inactivation in blood and streaky skin pigmentation compatible with functional mosaicism. Variants occurred de novo in ten individuals, of whom one was only mildly affected and transmitted it to her more severely affected daughter. The mutational spectrum comprises a 2-exon deletion, five truncating, one splice-site and three missense variants, the latter all located in the PHD2 domain and predicted to severely destabilize the domain structure. This observation supports the hypothesis of more severe variants in females contributing to gender-specific phenotypes in addition to or in combination with effects of X-inactivation and functional mosaicism. Therefore, our findings further delineate the clinical and mutational spectrum of female BFLS and provide further insights into possible genotype-phenotype correlations between females and males.

Keywords: Borjeson-Forssman-Lehmann syndrome; PHF6; X-chromosomal; de novo.

Abstract

While inherited hemizygous variants in PHF6 cause X-linked recessive Borjeson-Forssman-Lehmann syndrome (BFLS) in males, de novo heterozygous variants in females are associated with an overlapping but distinct phenotype, including moderate to severe intellectual disability, characteristic facial dysmorphism, dental, finger and toe anomalies and linear skin pigmentation. By personal communication with colleagues, we assembled eleven additional females with BFLS due to variants in PHF6. We confirm the distinct phenotype to include variable intellectual disability, recognizable facial dysmorphism and other anomalies. We observed skewed X-inactivation in blood and streaky skin pigmentation compatible with functional mosaicism. Variants occurred de novo in ten individuals, of whom one was only mildly affected and transmitted it to her more severely affected daughter. The mutational spectrum comprises a 2-exon deletion, five truncating, one splice-site and three missense variants, the latter all located in the PHD2 domain and predicted to severely destabilize the domain structure. This observation supports the hypothesis of more severe variants in females contributing to gender-specific phenotypes in addition to or in combination with effects of X-inactivation and functional mosaicism. Therefore, our findings further delineate the clinical and mutational spectrum of female BFLS and provide further insights into possible genotype-phenotype correlations between females and males.

Keywords: Borjeson-Forssman-Lehmann syndrome; PHF6; X-chromosomal; de novo.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Medical Genetics
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Uncontrolled Keywords:Genetics (clinical), Genetics, PHF6, X-chromosomal, de novo, Borjeson-Forssman-Lehmann syndrome
Language:English
Date:1 September 2022
Deposited On:08 Jun 2022 14:09
Last Modified:27 Apr 2024 01:37
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0009-9163
Additional Information:This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/cge.14173.
OA Status:Green
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1111/cge.14173
PubMed ID:35662002
  • Content: Accepted Version
  • Licence: Creative Commons: Attribution 4.0 International (CC BY 4.0)
  • Content: Accepted Version
  • Description: Supporting information