Makhbal, Zaya

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Makhbal, Zaya

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Makhbal Zaya

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Makhbal Zaya

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Анагаахын Шинжлэх Ухааны Үндэсний Их Сургууль

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Waardenburg Syndrome Type 4 in Mongolian Children: Genetic and Clinical Characterization
(2025-06)
Gombojav, Bayasgalan
;
Erdenechuluun, Jargalkhuu
;
Batsaikhan, Tserendulam
;
Danshiitsoodol, Narandalai
;
Makhbal, Zaya
Waardenburg syndrome (WS) is a rare genetic disorder that affects both hearing and pigmentation. The wide divergence of WS poses significant diagnostic and management challenges. This study investigated type 4 WS within an underrepresented Mongolian population. Whole-exome sequencing revealed that two unique heterozygous variants were identified in the SOX10 gene: c.393C>G (p.Asn131Lys) in a five-year-old female patient presenting with profound sensorineural hearing loss (SNHL), dystopia canthorum, and a white forelock; and c.535A>T (p.Lys179Ter) in a nine-year-old male patient presenting with profound SNHL, dystopia canthorum, and Hirschsprung's disease. Temporal bone imaging revealed abnormalities in the inner ear structure in both patients. The genotypic and phenotypic characteristics were meticulously delineated, incorporating the deleterious effects of these variants, as evaluated by multiple predictive tools and the American College of Medical Genetics and Genomics (ACMG) criteria. In addition, structural characterizations were also presented using AlphaFold. The findings of this study contribute valuable genetic data to the limited literature on type 4 WS within this ethnic group and highlight the importance of genetic testing and multidisciplinary care for this rare disorder in settings with limited resources.
Scopus© Citations 2
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A Unique SLC26A4 Mutation Spectrum in a Mongolian Enlarged Vestibular Aqueduct Cohort via Whole-Exome Sequencing: A Preliminary Study
(2026-06)
Erdenechuluun, Jargalkhuu
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Gombojav, Bayasgalan
;
Batsaikhan, Tserendulam
;
Lu, Yue-Sheng
;
Danshiitsoodol, Narandalai
Enlarged vestibular aqueduct (EVA) is a common inner ear malformation that causes sensorineural hearing loss. It is frequently associated with pathogenic variants in the SLC26A4 gene. This study aimed to investigate the genetic basis of hearing loss in Mongolian patients with EVA. Whole-exome sequencing was performed in 19 Mongolian patients from 15 unrelated families diagnosed with EVA with or without cochlear incomplete partition type II. All patients underwent high-resolution computed tomography of the temporal bone to confirm the diagnosis. Biallelic SLC26A4 pathogenic variants were identified in all 15 families, achieving a 100% diagnostic yield. The most frequent variant was c.919-2A>G (40%), followed by c.2027T>A (23.3%) and c.1318A>T (16.7%). The spectrum of variants includes population-specific variants found in East Asians (c.919-2A>G), North Asians (c.2027T>A), and Southwest Asians (c.716T>A), suggesting a unique mutation spectrum in this Mongolian cohort characterized by variants prevalent across various Eurasian populations, which remains to be confirmed in larger studies. Furthermore, correlation analyses on multi-ethnic allele frequencies of biallelic SLC26A4 genotypes demonstrated positive correlations with deaf cohorts of East Asian, North Asian, Northeast Asian, and Western Asian groups. Digenic inheritance (with pathogenic variants in FOXI1, KCNJ10, or EPHA2) was not observed, and there was no clear genotype-phenotype correlation between specific SLC26A4 genotypes and hearing levels or inner ear malformations. This study provides a comprehensive overview of the genetic landscape of EVA in the Mongolian population. The identification of biallelic SLC26A4 pathogenic variants in all families underscores the clinical role of this gene in EVA pathogenesis. The observed pan-ethnic mutation spectrum likely reflects the genetic diversity resulting from historical migrations of Mongolians.
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Unique spectra of deafness-associated mutations in Mongolians provide insights into the genetic relationships among Eurasian populations
(2018)
Erdenechuluun, Jargalkhuu
;
Lin, Yin-Hung
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Ganbat, Khongorzul
;
Bataakhuu, Delgermaa
;
Makhbal, Zaya
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.
Scopus© Citations 18
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Genetic Basis of Hearing Loss in Mongolian Patients: A Next-Generation Sequencing Study
(2024-09)
Gombojav, Bayasgalan
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Erdenechuluun, Jargalkhuu
;
Makhbal, Zaya
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Danshiitsoodol, Narandalai
;
Purevdorj, Erkhembulgan
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.
Scopus© Citations 2

Makhbal, Zaya

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