A novel MPZL2 c.68delC variant is associated with progressive hearing loss in Chinese population and literature review

Hearing restoration by gene replacement therapy for a multisite-expressed gene in a mouse model of human DFNB111 deafness

Gene therapy has made significant progress in the treatment of hereditary hearing loss. However, most research has focused on deafness-related genes that are primarily expressed in hair cells with less attention given to multisite-expressed deafness genes. MPZL2, the second leading cause of mild-to-moderate hereditary deafness, is widely expressed in different inner ear cells. We generated a mouse model with a deletion in the Mpzl2 gene, which displayed moderate and slowly progressive hearing loss, mimicking the phenotype of individuals with DFNB111. We developed a gene replacement therapy system mediated by AAV-ie for efficient transduction in various types of cochlear cells. AAV-ie-Mpzl2 administration significantly lowered the auditory brainstem response and distortion product otoacoustic emission thresholds of Mpzl2-/- mice for at least seven months. AAV-ie-Mpzl2 delivery restored the structural integrity in both outer hair cells and Deiters cells. This study suggests the potential of gene therapy for MPZL2-related deafness and provides a proof of concept for gene therapy targeting other deafness-related genes that are expressed in different cell populations in the cochlea.

Recurrent missense variant identified in two unrelated families with MPZL2-related hearing loss, expanding the variant spectrum associated with DFNB111

MPZL2-related hearing loss is a rare form of autosomal recessive hearing loss characterized by progressive, mild sloping to severe sensorineural hearing loss. Thirty-five previously reported patients had biallelic truncating variants in MPZL2, with the exception of one patient with a missense variant of uncertain significance and a truncating variant. Here, we describe the clinical characteristics and genotypes of five patients from four families with confirmed MPZL2-related hearing loss. A rare missense likely pathogenic variant [NM_005797.4(MPZL2):c.280C>T,p.(Arg94Trp)] located in exon 3 was confirmed to be in trans with a recurrent pathogenic truncating variant that segregated with hearing loss in three of the patients from two unrelated families. This is the first recurrent likely pathogenic missense variant identified in MPZL2. Apparently milder or later-onset hearing loss associated with rare missense variants in MPZL2 indicates that some missense variants in this gene may cause a milder phenotype than that resulting from homozygous or compound heterozygous truncating variants. This study, along with the identification of truncating loss of function and missense MPZL2 variants in several diverse populations, suggests that MPZL2-related hearing loss may be more common than previously appreciated and demonstrates the need for MPZL2 inclusion in hearing loss testing panels.

MPZL2-a common autosomal recessive deafness gene related to moderate sensorineural hearing loss in the Chinese population

BACKGROUND

Mutations in MPZL2, the characteristic genetic etiology of autosomal recessive deafness loci 111 (DFNB111), cause non-syndromic and moderate sensorineural hearing loss.

METHODS

In this study, we analyzed the phenotype and genotype of eight pedigrees consisting of 10 hearing loss patients with bi-allelic pathogenic or likely pathogenic variants in MPZL2. These patients were identified from a 3272 Chinese patient cohort who underwent genetic testing.

RESULTS

Apart from symmetrical and moderate sensorineural hearing loss, the MPZL2-related phenotype was characterized by progressive hearing loss with variation in the onset age (congenital defect to onset at the young adult stage). We determined that in the Chinese population, the genetic load of MPZL2 defects was 0.24% (8/3272) in patients diagnosed with hearing loss and 7.02% (8/114) in patients diagnosed with hereditary moderate sensorineural hearing loss caused by STRC, OTOA, OTOG, OTOGL, TECTA, MPZL2 and others. Three known MPZL2 variants (c.220C > T (p.Gln74*), c.68delC (p.Pro23Leufs*2), c.463delG (p.Ala155Leufs*10)) and a novel start loss variant (c.3G > T (p.Met1?)) were identified. MPZL2 c.220C > T was identified as the hotspot variant in the Chinese population and even in East Asia compared with c.72delA (p.Ile24Metfs*22) in European and West Asia through allele frequency.

CONCLUSIONS

We concluded that apart from moderate HL, progressive HL is another character of MPZL2-related HL. No specified variant was verified for the progression of HL, the penetrance and expressivity cannot be determined yet. A novel MPZL2 variant at the start codon was identified, enriching the variant spectrum of MPZL2. The hotspot variants of MPZL2 vary in different ethnicities. This study provides valuable data for the diagnosis, prognosis evaluation and genetic counseling of patients with moderate sensorineural hearing loss related to MPZL2.

[Genetic characteristic analysis of slight-to-moderate sensorineural hearing loss in children]

Objective:To analyze genetic factors and phenotype characteristics in pediatric population with slight-to-moderate sensorineural hearing loss. Methods:Children with slight-to-moderate sensorineural hearing loss of and their parents, enrolled from the Chinese Deafness Genome Project, were studied. Hearing levels were assessed using pure tone audiometry, behavioral audiometry, auditory steady state response（ASSR）, auditory brainstem response（ABR） thresholds, and deformed partial otoacoustic emission（DPOAE）. Classification of hearing loss is according to the 2022 American College of Medical Genetics and Genomics（ACMG） Clinical Practice Guidelines for Hearing Loss. Whole exome sequencing（WES） and deafness gene Panel testing were performed on peripheral venous blood from probands and validations were performed on their parents by Sanger sequencing. Results:All 134 patients had childhood onset, exhibiting bilateral symmetrical slight-to-moderate sensorineural hearing loss, as indicated by audiological examinations. Of the 134 patients, 29（21.6%） had a family history of hearing loss, and the rest were sporadic patients. Genetic causative genes were identified in 66（49.3%） patients. A total of 11 causative genes were detected, of which GJB2 was causative in 34 cases（51.5%）, STRC in 10 cases（15.1%）, MPZL2 gene in six cases（9.1%）, and USH2A in five cases（7.6%）.The most common gene detected in slight-to-moderate hearing loss was GJB2, with c. 109G>A homozygous mutation found in 16 cases（47.1%） and c. 109G>A compound heterozygous mutation in 9 cases（26.5%）. Conclusion:This study provides a crucial genetic theory reference for early screening and detection of mild to moderate hearing loss in children, highlighting the predominance of recessive inheritance and the significance of gene like GJB2, STRC, MPZL2, USH2A.

MPZL2 variant analysis with whole exome sequencing in a cohort of Chinese hearing loss patients

BACKGROUND

Hearing loss is a genetically heterogeneous disease with more than 100 genes identified. Pathogenic variants in the MPZL2 gene cause autosomal recessive non-syndromic hearing loss. MPZL2 patients showed mild to moderate progressive hearing loss with onset age around 10 years old. To date, four pathogenic variants have been identified.

AIMS

To explore the clinical characteristics and variants of MPZL2-related hearing loss, and summarize the prevalence rate in overall hearing loss patients.

MATERIAL AND METHODS

To determine the prevalence of MPZL2-related hearing loss in the Chinese population, we analyzed MPZL2 variants of whole exome sequencing data derived from a cohort of 385 hearing loss patients.

RESULTS

Overall, homozygous MPZL2 variants were identified in 5 sporadic cases (diagnostic rate = 1.30%). A novel missense variant c.52C > T;p.Leu18Phe was identified in one other patient with compound heterozygous mutations in MPZL2, but the pathogenicity was uncertain according to the American College of Medical Genetics guidelines (2015). A patient homozygous for the c.220C > T,p.Gln74Ter variant showed congenital profound hearing loss at all frequencies, a phenotype different from previous reports.

CONCLUSIONS

Our results enriched the mutation and phenotype spectrum of MPZL2-related hearing loss. Comparisons between allele frequencies of MPZL2:c.220C > T;p.Gln74Ter and other common deafness variants suggested that MPZL2:c.220C > T;p.Gln74Ter should be included in the group of common deafness variants for prescreening.

Development of a basement membrane gene signature and identification of the potential candidate therapeutic targets for pancreatic cancer

Background

Pancreatic cancer is a deadly cancer with a poor prognosis. In light of mounting evidence that basement membrane genes (BMGs) play a role in the development of cancer, we sought to examine the prognostic importance and role of BMGs in pancreatic ductal adenocarcinoma (PDAC) patients.

Methods

BMGs were obtained from previous top research studies. The clinical and messenger ribonucleic acid expression data were retrieved from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) data sets, respectively. Cox regression and least absolute shrinkage and selection operator (LASSO) regression analyses were used for the PDAC risk modeling and gene identification. The Kaplan-Meier method was used to compare outcomes between the low- and high-risk groups. Finally, we analyzed small-molecule drugs that could be used to target BMGs for treatment using the Enrichr data set and validated the function of the tubulointerstitial nephritis antigen (TINAG) in pancreatic cancer.

Results

We successfully constructed and validated a 7 BMG-based model to predict PDAC patient outcomes. Additionally, we discovered that 7 BMG-based model was an independent predictive factor for PDAC. According to our functional analysis, the majority of the signaling pathways enriched in BMGs were those connected to malignancy. Immune cell infiltration and immunological checkpoints were also linked to the BMG-based model. Further, we identified 5 small-molecule drugs that may be useful in treating PDAC patients. We also found that TINAG promoted cell proliferation in pancreatic cancer.

Conclusions

Our study extended understandings of how BMGs work in PDAC. We identified a credible predictive biomarker for PDAC patients' survival.