Homozygous Knockout of Cep250 Leads to a Relatively Late-Onset Retinal Degeneration and Sensorineural Hearing Loss in Mice

Purpose

Usher syndrome (USH) is the most common syndromic inherited retinal disease, causing retinitis pigmentosa and sensorineural hearing loss. We reported previously that a nonsense mutation in the centrosome-associated protein CEP250 gene (encoding C-Nap1) causes atypical USH in patients of Iranian Jewish origin. To better characterize CEP250, we aimed to generate and study a knockout (KO) mouse model for Cep250.

Methods

Mice heterozygous for a "knockout-first" Cep250 construct were generated and bred with Cre recombinase mice to generate the null allele and produce homozygous Cep250 KO mice. Retinal function was evaluated by full-field electroretinography (ffERG) at variable ages, and retinal structure changes were examined using histological analysis. Hearing thresholds were detected using auditory brainstem response (ABR) at the age of 20 months.

Results

The Cep250 KO mouse model was generated by activating a construct harboring a deletion of exons 6 and 7. At 6 months, the ffERG was normal, but it decreased gradually with age. For both photopic and scotopic ffERG responses, very low amplitudes were evident at 20 months. Histological analysis confirmed late-onset retinal degeneration. ABR tests illustrated that hearing threshold significantly increased at the age of 20 months.

Conclusions

Although most USH animal models have normal retinal function and structure, the Cep250 KO mouse model shows both retinal degeneration and hearing loss with a relatively late age of onset. This model may shed more light on CEP250-associated retinal and hearing deficits and represents an efficient platform for the development of treatment modalities for USH.

Translational Relevance

Our study demonstrates better understanding of Cep250-associated retinal and hearing disease in a mouse model and may help in developing more efficient gene therapy modalities.

NGLY1 Deficiency Zebrafish Model Manifests Abnormalities of the Nervous and Musculoskeletal Systems

Background: NGLY1 is an enigmatic enzyme with multiple functions across a wide range of species. In humans, pathogenic genetic variants in NGLY1 are linked to a variable phenotype of global neurological dysfunction, abnormal tear production, and liver disease presenting the rare autosomal recessive disorder N-glycanase deficiency. We have ascertained four NGLY1 deficiency patients who were found to carry a homozygous nonsense variant (c.1294G > T, p.Glu432*) in NGLY1.

Methods: We created an ngly1 deficiency zebrafish model and studied the nervous and musculoskeletal (MSK) systems to further characterize the phenotypes and pathophysiology of the disease.

Results: Nervous system morphology analysis has shown significant loss of axon fibers in the peripheral nervous system. In addition, we found muscle structure abnormality of the mutant fish. Locomotion behavior analysis has shown hypersensitivity of the larval ngly1^(−/−) fish during stress conditions.

Conclusion: This first reported NGLY1 deficiency zebrafish model might add to our understanding of NGLY1 role in the development of the nervous and MSK systems. Moreover, it might elucidate the natural history of the disease and be used as a platform for the development of novel therapies.

The Genetics of Usher Syndrome in the Israeli and Palestinian Populations

Purpose

Usher syndrome (USH) is the most common cause for deaf-blindness. It is genetically and clinically heterogeneous and prevalent in populations with high consanguinity rate. We aim to characterize the set of genes and mutations that cause USH in the Israeli and Palestinian populations.

Methods

Seventy-four families with USH were recruited (23 with USH type 1 [USH1], 33 with USH2, seven with USH3, four with atypical USH, and seven families with an undetermined USH type). All affected subjects underwent a full ocular evaluation. A comprehensive genetic analysis, including Sanger sequencing for the detection of founder mutations, homozygosity mapping, and whole exome sequencing in large families was performed.

Results

In 79% of the families (59 out of 74), an autosomal recessive inheritance pattern could be determined. Mutation detection analysis led to the identification of biallelic causative mutations in 51 (69%) of the families, including 21 families with mutations in USH2A, 17 in MYO7A, and seven in CLRN1. Our analysis revealed 28 mutations, 11 of which are novel (including c.802G>A, c.8558+1G>T, c.10211del, and c.14023A>T in USH2A; c.285+2T>G, c.2187+1G>T, c.3892G>A, c.5069_5070insC, c.5101C>T, and c.6196C>T in MYO7A; and c.15494del in GPR98).

Conclusions

We report here novel homozygous mutations in various genes causing USH, extending the spectrum of causative mutations. We also prove combined sequencing techniques as useful tools to identify novel disease-causing mutations. To the best of our knowledge, this is the largest report of a genetic analysis of Israeli and Palestinian families (n = 74) with different USH subtypes.

Identification of genomic deletions causing inherited retinal degenerations by coverage analysis of whole exome sequencing data

BACKGROUND

Inherited retinal degenerations (IRDs) are a common cause of visual disturbance with a high clinical and genetic heterogeneity. Recent sequencing techniques such as whole exome sequencing (WES) contribute to the discovery of novel genes. The aim of the current study was to use WES data to identify large deletions that include at least one exon in known IRD genes.

METHODS

Patients diagnosed with IRDs underwent a comprehensive ophthalmic evaluation. WES was performed using the NimbleGen V2 paired-end kit and HiSeq 2000. An analysis of exon coverage data was performed on 60 WES samples. Exonic deletions were verified by 'PCR walking' analysis.

RESULTS

We analysed data obtained from 60 WES samples of index patients with IRDs. By calculating the average coverage for all exons in the human genome, we were able to identify homozygous and hemizygous deletions of at least one exon in six families (10%), including a single-exon deletion in EYS, deletions of three consecutive exons in MYO7A and NPHP4, deletions of four and eight consecutive exons in RPGR and a multigene deletion on the X-chromosome, including CHM. By using PCR-walking analysis, we were able to identify the borders of five of the deletions and to screen our set of patients for these deletions.

CONCLUSIONS

We performed here a comprehensive analysis of WES data as a tool for identifying large genomic deletions in patients with IRDs. Our analysis indicates that large deletions are relatively frequent (about 10% of our WES cohort) and should be screened when analysing WES data.

Trans-fascial laparoscopic mesh fixation: a procedural comparison using the standard suture passer versus iMESH stitcher™ device

INTRODUCTION

Laparoscopic mesh repair has become an increasingly common method for repairing incisional hernias. The current method for fixating mesh to the abdominal wall includes tacking the mesh to the peritoneum and fascia and suturing the mesh to the fascia with trans-fascial sutures. The iMESH Stitcher™ is a stitching device developed to both simplify and expedite this procedure by passing the suture from one arm of the iMESH stitcher™ to the other. The device enables a stitch to be created in three quick moves using only one hand. We compared both the efficacy and procedure time of trans-fascial mesh fixation when performed with the iMESH stitcher™ as compared to the standard suture passer method.

METHODS

A mesh patch was installed on the internal abdominal wall of two pigs. Surgical residents and Medical students were participants in the study and were trained in both techniques. Each participant was asked to perform six fixations with each technique. The procedural time required for both fixation techniques was recorded. Participants were asked to assess subjectively the relative difficulty of each technique on a scale of 1-10 (10 = most difficult).

RESULTS

Sixteen residents and students performed a total of 12 mesh fixations, each performing 6 fixations with each technique. Average mesh fixation suture time using the suture passer technique was 44 s for residents and 47 s for students. Average fixation suture time using the iMESH stitcherTM was 17 s for residents and 15 s for students. The average difficulty score for the suture passer technique was 6.1 as compared to 2.9 with iMESH stitcher™.

CONCLUSION

Trans-fascial fixation with the iMESH Stitcher™ took significantly less time than the standard suture passer method. The iMESH Stitcher™ significantly simplifies the procedure of transfascial fixation and potentially reduces technical difficulties.

Determinants of pancreatic beta-cell regeneration

Recent studies have revealed a surprising plasticity of pancreatic beta-cell mass. beta-cell mass is now recognized to increase and decrease in response to physiological demand, for example during pregnancy and in insulin-resistant states. Moreover, we and others have shown that mice recover spontaneously from diabetes induced by killing of 70-80% of beta-cells, by beta-cell regeneration. The major cellular source for new beta-cells following specific ablation, as well as during normal homeostatic maintenance of adult beta-cells, is proliferation of differentiated beta-cells. More recently, it was shown that one form of severe pancreatic injury, ligation of the main pancreatic duct, activates a population of embryonic-type endocrine progenitor cells, which can differentiate into new beta-cells. The molecular triggers for enhanced beta-cell proliferation during recovery from diabetes and for activation of embryonic-type endocrine progenitors remain unknown and represent key challenges for future research. Taken together, recent data suggest that regenerative therapy for diabetes may be a realistic goal.