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We conducted zircon U–Pb dating and geochemical analyses for the Qianjinchang (QJC) pluton in the Xi Ujimqi, Northeast China, with an aim to determine their ages, petrogenesis, and sources. The QJC pluton consists of coarse/medium‐grained biotite monzogranite in the core and fine‐grained biotite granodiorite in the rim; those rocks intrude into quartz diorite but are intruded by minor intrusive phases, including small biotite syenogranite, diorite bodies, late diorite, granodiorite, granite, and pegmatite dykes. Our new laser ablation inductively coupled plasma mass spectrometry zircon U–Pb data indicate that the QJC composite pluton composed of 2 phases of magmatic activities, with the ages of 301~313 Ma for the quartz diorite, 283 ± 1 Ma for the biotite granodiorite, 280 ± 1 Ma for the biotite syenogranite, and 280 ± 2 Ma for the diorite dyke. Hf isotopic analyses for the quartz diorite sample show εHf (t) = 3.75 to 11.72, with 2‐stage Hf model age (TDM2) ranging 568–1,078 Ma. The biotite syenogranite sample also shows a depleted εHf (t) = 4.47 to 8.71, with TDM2 ranging 745–1,015 Ma, suggesting the major involvement of juvenile crustal components. The various εHf values of the QJC pluton indicate a hybrid magma source of juvenile material with old crustal component, and the TDM2 values increase from the Carboniferous to Permian, which suggests an increasing proportion of old continental material during this period. Petrological and geochemical characteristics of the biotite granodiorite and biotite monzogranite samples suggest that they are S‐type granites and derived from partial melting of the clay‐poor, plagioclase‐rich psammitic source, produced at low‐medium pressure. The biotite syenogranite sample belongs to alkaline and shoshonitic series and probably formed by a hybridization process between basaltic magma and old continental components. Combined with previous studies on the contemporaneous magma‐tectonic activities in the Xilinhot microcontinent, we suggest that the QJC pluton formed in a postcollisional setting. [ABSTRACT FROM AUTHOR]

Background/objective: The genetic landscape of sensorineural hearing impairment (SNHI) varies across populations. In Mongolia, previous studies have shown a lower prevalence of GJB2 mutations and a higher frequency of variants in other deafness-related genes. This study aimed to investigate the genetic variants associated with idiopathic SNHI in Mongolian patients., Methods: We utilized the next-generation sequencing for investigating the causative mutations in 99 Mongolian patients with SNHI., Results: We identified pathogenic variants in 53 of the 99 SNHI patients (54%), with SLC26A4 being the most frequently mutated gene. The c.919-2A>G variant in SLC26A4 was the most prevalent, accounting for 46.2% of the mutant alleles. In addition, we identified 19 other known and 21 novel mutations in a total of 21 SNHI genes in autosomal recessive or dominant inheritance patterns., Conclusions: Our findings expand the understanding of the genetic landscape of SNHI in Mongolia and highlight the importance of considering population-specific variations in genetic testing and counseling for SNHI.

Recessive variants in GJB2 are the most common genetic cause of sensorineural hearing impairment. However, in many patients, only one variant in the GJB2 coding region is identified using conventional sequencing strategy (eg, Sanger sequencing), resulting in nonconfirmative diagnosis. Conceivably, there might be other unidentified pathogenic variants in the noncoding region of GJB2 or other deafness-causing genes in these patients. To address this, a next-generation sequencing-based diagnostic panel targeting the entire GJB2 gene and the coding regions of 158 other known deafness-causing genes was designed and applied to 95 patients with nonsyndromic sensorineural hearing impairment (including 81 Han Taiwanese and 14 Mongolian patients) in whom only a single GJB2 variant had been detected using conventional Sanger sequencing. The panel confirmed the genetic diagnosis in 24 patients (25.3%). Twenty-two of them had causative variants in several deafness-causing genes other than GJB2, including MYO15A, MYO7A, TECTA, POU4F3, KCNQ4, SLC26A4, OTOF, MT-RNR1, MITF, WFS1, and USH2A. The other two patients had causative variants in GJB2, including a Taiwanese patient with a mosaic maternal uniparental disomy c.235delC variant (approximately 69% mosaicism) and a Mongolian patient with compound heterozygous c.35dupG and c.35delG variants, which occurred at the same site. This study demonstrates the utility of next-generation sequencing in clarifying the genetic diagnosis of hearing-impaired patients with nonconfirmative GJB2 genotypes on conventional genetic examinations., (Copyright © 2021 Association for Molecular Pathology and American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Genetic factors are an important cause of idiopathic sensorineural hearing impairment (SNHI). From the epidemiological perspective, mutations of three deafness genes: GJB2, SLC26A4, and MT-RNR1, are much more prevalent than those of other genes worldwide. However, mutation spectra of common deafness genes differ remarkably across different populations. Here, we performed comprehensive genetic examination and haplotype analyses in 188 unrelated Mongolian families with idiopathic SNHI, and compared their mutation spectra and haplotypes to those of other European and Asian cohorts. We confirmed genetic diagnoses in 18 (9.6%) of the 188 families, including 13 with bi-allelic GJB2 mutations, three with bi-allelic SLC26A4 mutations, and two with homoplasmic MT-RNR1 m.1555A>G mutation. Moreover, mono-allelic mutations were identified in 17 families (9.0%), including 14 with mono-allelic GJB2 mutations and three with mono-allelic SLC26A4 mutations. Interestingly, three GJB2 mutations prevalent in other populations, including c.35delG in Caucasians, c.235delC in East Asians, and c.-23+1G>A in Southwest and South Asians, were simultaneously detected in Mongolian patients. Haplotype analyses further confirmed founder effects for each of the three mutations, indicating that each mutation derived from its ancestral origin independently. By demonstrating the unique spectra of deafness-associated mutations, our findings may have important clinical and scientific implications for refining the molecular diagnostics of SNHI in Mongolian patients, and for elucidating the genetic relationships among Eurasian populations., Competing Interests: The authors have declared that no competing interests exist.