ABSTRACT
Hepatocyte growth factor (HGF) is a multifunctional protein that signals through the MET receptor. HGF stimulates cell proliferation, cell dispersion, neuronal survival, and wound healing. In the inner ear, levels of HGF must be fine-tuned for normal hearing. In mice, a deficiency of HGF expression limited to the auditory system, or an overexpression of HGF, causes neurosensory deafness. In humans, noncoding variants in HGF are associated with nonsyndromic deafness DFNB39 However, the mechanism by which these noncoding variants causes deafness was unknown. Here, we reveal the cause of this deafness using a mouse model engineered with a noncoding intronic 10 bp deletion (del10) in Hgf Male and female mice homozygous for del10 exhibit moderate-to-profound hearing loss at 4 weeks of age as measured by tone burst auditory brainstem responses. The wild type (WT) 80 mV endocochlear potential was significantly reduced in homozygous del10 mice compared with WT littermates. In normal cochlea, endocochlear potentials are dependent on ion homeostasis mediated by the stria vascularis (SV). Previous studies showed that developmental incorporation of neural crest cells into the SV depends on signaling from HGF/MET. We show by immunohistochemistry that, in del10 homozygotes, neural crest cells fail to infiltrate the developing SV intermediate layer. Phenotyping and RNAseq analyses reveal no other significant abnormalities in other tissues. We conclude that, in the inner ear, the noncoding del10 mutation in Hgf leads to developmental defects of the SV and consequently dysfunctional ion homeostasis and a reduction in the EP, recapitulating human DFNB39 nonsyndromic deafness.SIGNIFICANCE STATEMENT Hereditary deafness is a common, clinically and genetically heterogeneous neurosensory disorder. Previously, we reported that human deafness DFNB39 is associated with noncoding variants in the 3'UTR of a short isoform of HGF encoding hepatocyte growth factor. For normal hearing, HGF levels must be fine-tuned as an excess or deficiency of HGF cause deafness in mouse. Using a Hgf mutant mouse with a small 10 bp deletion recapitulating a human DFNB39 noncoding variant, we demonstrate that neural crest cells fail to migrate into the stria vascularis intermediate layer, resulting in a significantly reduced endocochlear potential, the driving force for sound transduction by inner ear hair cells. HGF-associated deafness is a neurocristopathy but, unlike many other neurocristopathies, it is not syndromic.
Subject(s)
Cochlea/physiopathology , Evoked Potentials, Auditory, Brain Stem/genetics , Hearing Loss, Sensorineural/genetics , Hepatocyte Growth Factor/genetics , Neural Crest/growth & development , Stria Vascularis/pathology , Animals , Cell Count , Ear, Inner/abnormalities , Female , Hair Cells, Auditory , Hearing Loss, Sensorineural/pathology , Homeostasis , Humans , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Neural Crest/pathology , RNA ProbesABSTRACT
We isolated egl-13 mutants in which the pi cells of the Caenorhabditis elegans uterus initially appeared to develop normally but then underwent an extra round of cell division. The data suggest that egl-13 is required for maintenance of the pi cell fate.
Subject(s)
Caenorhabditis elegans Proteins/physiology , Caenorhabditis elegans/genetics , Cell Lineage/physiology , Transcription Factors/physiology , Uterus/cytology , Amino Acid Sequence , Animals , Caenorhabditis elegans/cytology , Caenorhabditis elegans Proteins/chemistry , Caenorhabditis elegans Proteins/genetics , Female , Molecular Sequence Data , Transcription Factors/chemistry , Transcription Factors/geneticsABSTRACT
The fusion of the Caenorhabditis elegans uterine anchor cell (AC) with the uterine-seam cell (utse) is an excellent model system for studying cell-cell fusion, which is essential to animal development. We obtained an egg-laying defective (Egl) mutant in which the AC fails to fuse with the utse. This defect is highly specific: other aspects of utse development and other cell fusions appear to occur normally. We find that defect is due to a missense mutation in the nsf-1 gene, which encodes N-ethylmaleimide-sensitive factor (NSF), an intracellular membrane fusion factor. There are two NSF-1 isoforms, which are expressed in distinct tissues through two separate promoters. NSF-1L is expressed in the uterus, including the AC. We find that nsf-1 is required cell-autonomously in the AC for its fusion with the utse. Our results establish AC fusion as a paradigm for studying cell fusion at single cell resolution and demonstrate that the NSF ATPase is a key player in this process.