Homozygous loss-of-function mutations in MNS1 cause laterality defects and likely male infertility.

Asaf Ta‐Shma ,Alper Gezdirici,Miriam Schmidts,Israel Amirav,Rim Hjeij,Heymut Omran,Niki T Loges,Avraham Shaag,Zeev Perles,Ronald Roepman,Oded Breuer,Alaa Darwish,Isabella Aprea,Gerard W Dougherty,Revital Abitbul,Christine Edelbusch,Tabea Nöthe-Menchen,Ibrahim Abu Zahira,Nael Elias,Dinu Antony,Orly Elpeleg,Dorus A Mans,Sabrina Spittler,Petra Pennekamp,Friederike Stuhlmann,Sandra Cindrić,Heike Olbrich,Elif Yılmaz Güleç ,Stef J.f Letteboer ,Azaria J.j.t Rein

doi:10.1371/journal.pgen.1007602

Abstract

The clinical spectrum of ciliopathies affecting motile cilia spans impaired mucociliary clearance in the respiratory system, laterality defects including heart malformations, infertility and hydrocephalus. Using linkage analysis and whole exome sequencing, we identified two recessive loss-of-function MNS1 mutations in five individuals from four consanguineous families: 1) a homozygous nonsense mutation p.Arg242* in four males with laterality defects and infertility and 2) a homozygous nonsense mutation p.Gln203* in one female with laterality defects and recurrent respiratory infections additionally carrying homozygous mutations in DNAH5. Consistent with the laterality defects observed in these individuals, we found Mns1 to be expressed in mouse embryonic ventral node. Immunofluorescence analysis further revealed that MNS1 localizes to the axonemes of respiratory cilia as well as sperm flagella in human. In-depth ultrastructural analyses confirmed a subtle outer dynein arm (ODA) defect in the axonemes of respiratory epithelial cells resembling findings reported in Mns1-deficient mice. Ultrastructural analyses in the female carrying combined mutations in MNS1 and DNAH5 indicated a role for MNS1 in the process of ODA docking (ODA-DC) in the distal respiratory axonemes. Furthermore, co-immunoprecipitation and yeast two hybrid analyses demonstrated that MNS1 dimerizes and interacts with the ODA docking complex component CCDC114. Overall, we demonstrate that MNS1 deficiency in humans causes laterality defects (situs inversus) and likely male infertility and that MNS1 plays a role in the ODA-DC assembly.

Highlights

Cilia assemble on most cell types of the human body to perform diverse biological roles [1]
No clear explanation is yet provided for the correct establishment of the leftright body asymmetry in human, animal studies have clearly shown that tiny-hair-like organelles in the ventral node of the embryo—called motile nodal monocilia—beat regularly and play an important role in this process
We describe two loss-of-function variants in MNS1 in individuals suffering from laterality defects and infertility

Summary

Introduction

Cilia assemble on most cell types of the human body to perform diverse biological roles [1]. Motile cilia and flagella exhibit several tissue and cell-type specific functions. Establishment of the left-right body axis in vertebrates is an evolutionarily conserved process for which in mammals the embryonic node plays an essential role. Analyses of mouse mutants affected by impaired left-right body axes’ development have proven that dysmotility or abnormal differentiation of nodal monocilia correlate directly with laterality defects [4]. Laterality defects can be observed as a consequence of defective signal reception at the embryonic node and/or defects within the left-right patterning signaling pathways itself such as NODAL, Bmp or FGF signaling [3]. Congenital heart disease (CHD) can be frequently observed [5,6]

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