Genetic Landscape of Hearing Loss in the Caribbean: A Narrative Review.

The Caribbean region has a diverse population of about 40 million people, spread over 13 sovereign states. This review aims to describe the existing studies on hereditary hearing loss (HL) in the Caribbean population. We systematically reviewed scientific articles on HL prevalence, genetic causes, technology use, and environmental effects in Caribbean nations and the Caribbean diaspora in the United States. Key findings show that HL rates, with diverse genetic variables, vary across Puerto Rico, Cuba, and the Dominican Republic. Local resources and technology have been used to diagnose HL, particularly in rural areas. Environmental factors tend to affect HL prevalence in various regions. This literature review of Caribbean-focused studies helps guide future research and healthcare strategies, particularly concerning genetic drift caused by migration to the United States. Understanding these factors can help diagnose and treat HL in America's diverse population.

Recurrent ATP1A1 variant Gly903Arg causes developmental delay, intellectual disability, and autism.

ATP1A1 encodes a sodium-potassium ATPase that has been linked to several neurological diseases. Using exome and genome sequencing, we identified the heterozygous ATP1A1 variant NM_000701.8: c.2707G>A;p.(Gly903Arg) in two unrelated children presenting with delayed motor and speech development and autism. While absent in controls, the variant occurred de novo in one proband and co-segregated in two affected half-siblings, with mosaicism in the healthy mother. Using a specific ouabain resistance assay in mutant transfected HEK cells, we found significantly reduced cell viability. Demonstrating loss of ATPase function, we conclude that this novel variant is pathogenic, expanding the phenotype spectrum of ATP1A1.

ADAMTSL2 mutations determine the phenotypic severity in geleophysic dysplasia.

Geleophysic dysplasia-1 (GD1) is an autosomal recessive disorder caused by ADAMTS-like 2 (ADAMTSL2) variants. It is characterized by distinctive facial features, limited joint mobility, short stature, brachydactyly, and life-threatening cardiorespiratory complications. The clinical spectrum spans from perinatal lethality to milder adult phenotypes. We developed and characterized cellular and mouse models, to replicate the genetic profile of a patient who is compound heterozygous for 2 ADAMTSL2 variants, namely p.R61H and p.A165T. The impairment of ADAMTSL2 secretion was observed in both variants, but p.A165T exhibited a more severe impact. Mice carrying different allelic combinations revealed a spectrum of phenotypic severity, from lethality in knockout homozygotes to mild growth impairment observed in adult p.R61H homozygotes. Homozygous and hemizygous p.A165T mice survived but displayed severe respiratory and cardiac dysfunction. The respiratory dysfunction mainly affected the expiration phase, and some of these animals had microscopic post-obstructive pneumonia. Echocardiograms and MRI studies revealed a significant systolic dysfunction, accompanied by a reduction of the aortic root size. Histology verified the presence of hypertrophic cardiomyopathy with myocyte hypertrophy, chondroid metaplasia, and mild interstitial fibrosis. This study revealed a substantial correlation between the degree of impaired ADAMTSL2 secretion and the severity of the observed phenotype in GD1.

Genetic heterogeneity in hereditary hearing loss: Potential role of kinociliary protein TOGARAM2.

Hearing loss (HL) is a heterogenous trait with pathogenic variants in more than 200 genes that have been discovered in studies involving small and large HL families. Over one-third of families with hereditary HL remain etiologically undiagnosed after screening for mutations in the recognized genes. Genetic heterogeneity complicates the analysis in multiplex families where variants in more than one gene can be causal in different individuals even in the same sibship. We employed exome or genome sequencing in at least two affected individuals with congenital or prelingual-onset, severe to profound, non-syndromic, bilateral sensorineural HL from four multiplex families. Bioinformatic analysis was performed to identify variants in known and candidate deafness genes. Our results show that in these four families, variants in a single HL gene do not explain HL in all affected family members, and variants in another known or candidate HL gene were detected to clarify HL in the entire family. We also present a variant in TOGARAM2 as a potential cause underlying autosomal recessive non-syndromic HL by showing its presence in a family with HL, its expression in the cochlea and the localization of the protein to cochlear hair cells. Conclusively, analyzing all affected family members separately can serve as a good source for the identification of variants in known and novel candidate genes for HL.

SNUPN deficiency causes a recessive muscular dystrophy due to RNA mis-splicing and ECM dysregulation.

SNURPORTIN-1, encoded by SNUPN, plays a central role in the nuclear import of spliceosomal small nuclear ribonucleoproteins. However, its physiological function remains unexplored. In this study, we investigate 18 children from 15 unrelated families who present with atypical muscular dystrophy and neurological defects. Nine hypomorphic SNUPN biallelic variants, predominantly clustered in the last coding exon, are ascertained to segregate with the disease. We demonstrate that mutant SPN1 failed to oligomerize leading to cytoplasmic aggregation in patients' primary fibroblasts and CRISPR/Cas9-mediated mutant cell lines. Additionally, mutant nuclei exhibit defective spliceosomal maturation and breakdown of Cajal bodies. Transcriptome analyses reveal splicing and mRNA expression dysregulation, particularly in sarcolemmal components, causing disruption of cytoskeletal organization in mutant cells and patient muscle tissues. Our findings establish SNUPN deficiency as the genetic etiology of a previously unrecognized subtype of muscular dystrophy and provide robust evidence of the role of SPN1 for muscle homeostasis.

Triple Primary Cancers: An Analysis of Genetic and Environmental Factors.

The occurrence of multiple primary cancers (MPC) is thought to reflect increased cancer susceptibility in patients due to a combination of genetic and environmental factors. Here we conducted a retrospective review of 2,894 consecutive patients evaluated at a single institution and identified 31 (1.14%) individuals with a history of three or more primary cancers, then analyzed the genetic and environmental influences associated with their propensity for developing malignancies. We found that 35.5% of patients had a hereditary cancer syndrome (HCS), with high penetrance HCS in 72.7% of cases, suggesting that monogenic causes underly a significant proportion of triple primary cancer risk. Analysis of cancer frequencies found that the diagnosis of breast cancer was associated with a significantly lower likelihood of HCS, while the diagnosis of colorectal, prostate, and pancreas cancer was associated with a significantly higher likelihood of HCS. Comparison of HCS-positive and HCS-negative patients revealed similar demographic characteristics, mean age at first diagnosis, and family history of cancer. Moreover, no significant differences in lifestyle behaviors, occupational exposures, chronic health conditions, or treatment with chemotherapy and radiation were observed between HCS-positive and -negative groups, though outliers in tobacco smoking, as well as systemic treatment after both first and second primary cancers were observed. These findings indicate a robust contribution of HCS to cancer susceptibility among patients with triple primary cancers while environmental influences were less evident. This emphasizes the need for larger MPC cohorts incorporating additional genetic and environmental factors to more comprehensively characterize drivers of cancer risk. PREVENTION RELEVANCE: In patients with three or more primary cancers, genetic predisposition explained a significant proportion of cases; however, treatment history, lifestyle habits, and other exposures appeared to play a less significant role. This highlights the value of early genetic screening and the need to develop more sensitive markers of cancer susceptibility. See related Spotlight, p. 193.

EFEMP1 haploinsufficiency causes a Marfan-like hereditary connective tissue disorder.

Phenotypic features of a hereditary connective tissue disorder, including craniofacial characteristics, hyperextensible skin, joint laxity, kyphoscoliosis, arachnodactyly, inguinal hernia, and diverticulosis associated with biallelic pathogenic variants in EFEMP1 have been previously described in four patients. Genome sequencing on a proband and her mother with comparable phenotypic features revealed that both patients were heterozygous for a stop-gain variant c.1084C>T (p.Arg362*). Complementary RNA-seq on fibroblasts revealed significantly reduced levels of mutant EFEMP1 transcript. Considering the absence of other molecular explanations, we extrapolated that EFEMP1 could be the cause of the patient's phenotypes. Furthermore, nonsense-mediated decay was demonstrated for the mutant allele as the principal mechanism for decreased levels of EFEMP1 mRNA. We provide strong clinical and genetic evidence for the haploinsufficiency of EFEMP1 due to nonsense-medicated decay to cause severe kyphoscoliosis, generalized hypermobility of joints, high and narrow arched palate, and potentially severe diverticulosis. To the best of our knowledge, this is the first report of an autosomal dominant EFEMP1-associated hereditary connective tissue disorder and therefore expands the phenotypic spectrum of EFEMP1 related disorders.

Identification of novel MYH14 variants in families with autosomal dominant sensorineural hearing loss.

Autosomal dominant sensorineural hearing loss (ADSNHL) is a genetically heterogeneous disorder caused by pathogenic variants in various genes, including MYH14. However, the interpretation of pathogenicity for MYH14 variants remains a challenge due to incomplete penetrance and the lack of functional studies and large families. In this study, we performed exome sequencing in six unrelated families with ADSNHL and identified five MYH14 variants, including three novel variants. Two of the novel variants, c.571G > C (p.Asp191His) and c.571G > A (p.Asp191Asn), were classified as likely pathogenic using ACMG and Hearing Loss Expert panel guidelines. In silico modeling demonstrated that these variants, along with p.Gly1794Arg, can alter protein stability and interactions among neighboring molecules. Our findings suggest that MYH14 causative variants may be more contributory and emphasize the importance of considering this gene in patients with nonsyndromic mainly post-lingual severe form of hearing loss. However, further functional studies are needed to confirm the pathogenicity of these variants.

RExPRT: a machine learning tool to predict pathogenicity of tandem repeat loci.

Expansions of tandem repeats (TRs) cause approximately 60 monogenic diseases. We expect that the discovery of additional pathogenic repeat expansions will narrow the diagnostic gap in many diseases. A growing number of TR expansions are being identified, and interpreting them is a challenge. We present RExPRT (Repeat EXpansion Pathogenicity pRediction Tool), a machine learning tool for distinguishing pathogenic from benign TR expansions. Our results demonstrate that an ensemble approach classifies TRs with an average precision of 93% and recall of 83%. RExPRT's high precision will be valuable in large-scale discovery studies, which require prioritization of candidate loci for follow-up studies.

Two novel heterozygous exonic deletions lead to Chanarin-Dorfman syndrome in a patient with congenital ichthyosis, sensorineural hearing loss, and liver dysfunction.

Chanarin-Dorfman syndrome is an autosomal recessively inherited disorder characterized by ichthyosis, sensorineural hearing loss, and hepatic dysfunction. We report on a 60-year-old female of Venezuelan descent who presented with congenital ichthyosis, progressive sensorineural hearing loss, and liver cirrhosis. We identify a heterozygous copy number deletion involving exon 1 and another heterozygous deletion involving exon 3 of the ABHD5 gene. Exon 2 is preserved. Both deletions were confirmed with RT-PCR. RNAseq from peripheral blood shows a reduction of ABHD5 expression overall and an absence of exon 3 expression, confirming the deleterious effects of the identified deletions. We present exonic deletions as a potentially common type of ABHD5 variation.

Dispersed DNA variants underlie hearing loss in South Florida's minority population.

BACKGROUND: We analyzed the genetic causes of sensorineural hearing loss in racial and ethnic minorities of South Florida by reviewing demographic, phenotypic, and genetic data on 136 patients presenting to the Hereditary Hearing Loss Clinic at the University of Miami. In our retrospective chart review, of these patients, half self-identified as Hispanic, and the self-identified racial distribution was 115 (86%) White, 15 (11%) Black, and 6 (4%) Asian. Our analysis helps to reduce the gap in understanding the prevalence, impact, and genetic factors related to hearing loss among diverse populations. RESULTS: The causative gene variant or variants were identified in 54 (40%) patients, with no significant difference in the molecular diagnostic rate between Hispanics and Non-Hispanics. However, the total solve rate based on race was 40%, 47%, and 17% in Whites, Blacks, and Asians, respectively. In Non-Hispanic Whites, 16 different variants were identified in 13 genes, with GJB2 (32%), MYO7A (11%), and SLC26A4 (11%) being the most frequently implicated genes. In White Hispanics, 34 variants were identified in 20 genes, with GJB2 (22%), MYO7A (7%), and STRC-CATSPER2 (7%) being the most common. In the Non-Hispanic Black cohort, the gene distribution was evenly dispersed, with 11 variants occurring in 7 genes, and no variant was identified in 3 Hispanic Black probands. For the Asian cohort, only one gene variant was found out of 6 patients. CONCLUSION: This study demonstrates that the diagnostic rate of genetic studies in hearing loss varies according to race in South Florida, with more heterogeneity in racial and ethnic minorities. Further studies to delineate deafness gene variants in underrepresented populations, such as African Americans/Blacks from Hispanic groups, are much needed to reduce racial and ethnic disparities in genetic diagnoses.

Novel GPR156 variants confirm its role in moderate sensorineural hearing loss.

Hereditary hearing loss (HL) is a genetically heterogeneous disorder affecting people worldwide. The implementation of advanced sequencing technologies has significantly contributed to the identification of novel genes involved in HL. In this study, probands of two Turkish families with non-syndromic moderate HL were subjected to exome sequencing. The data analysis identified the c.600G > A (p.Thr200Thr) and c.1863dupG (p.His622fs) variants in GPR156, which co-segregated with the phenotype as an autosomal recessive trait in the respective families. The in silico predictions and a minigene assay showed that the c.600G > A variant disrupts mRNA splicing. This gene belongs to the family of G protein-coupled receptors whose function is not well established in the inner ear. GPR156 variants have very recently been reported to cause HL in three families. Our study from a different ethnic background confirms GPR156 as a bona fide gene involved in HL in humans. Further investigation towards the understanding of the role of GPCRs in the inner ear is warranted.

6 February 2023, orthopedic experience in Kahramanmaras earthquake and surgical decision in patients with crush syndrome.

BACKGROUND: The decision of fasciotomy or amputation in crush syndrome is controversial and challenging for surgeons. We aimed to share our experiences after the Kahramanmaras earthquake, to predict the severity of crush syndrome and mortality, and to guide the surgical decision. METHODS: The clinical data of patients during their first week of hospitalization were analyzed retrospectively. Totally, 233 crush syndrome patients were included. Demographic data, physical and laboratory findings, surgical treatments, and outcomes were recorded. RESULTS: The mean time under the rubble was 41.89 ± 29.75 h. Fasciotomy and amputation were performed in 41 (17.6%) and 72 (30.9%) patients. One hundred and two patients (56.7%) underwent hemodialysis. Fifteen patients (6.4%) died. Lower extremity injury, abdominal trauma, and thoracic trauma were associated with mortality. Mortality was significantly increased in patients with thigh injuries (p = 0.028). The mean peak CK concentration was 69.817.69 ± 134.812.04 U/L. Peak CK concentration increased substantially with amputation (p = 0.002), lower limb injury (p < 0.001), abdominal trauma (p = 0.011), and thoracic trauma (p = 0.048). CONCLUSIONS: Thigh injury is associated with the severity of crush syndrome and mortality. Late fasciotomy should not be preferred in crush syndrome. Amputation is life-saving, especially in desperate lower extremity injuries.

Genome sequencing identifies coding and non-coding variants for non-syndromic hearing loss.

Hearing loss (HL) is a common heterogeneous trait that involves variants in more than 200 genes. In this study, we utilized exome (ES) and genome sequencing (GS) to effectively identify the genetic cause of presumably non-syndromic HL in 322 families from South and West Asia and Latin America. Biallelic GJB2 variants were identified in 58 probands at the time of enrollment these probands were excluded. In addition, upon review of phenotypic findings, 38/322 probands were excluded based on syndromic findings at the time of ascertainment and no further evaluation was performed on those samples. We performed ES as a primary diagnostic tool on one or two affected individuals from 212/226 families. Via ES we detected a total of 78 variants in 30 genes and showed their co-segregation with HL in 71 affected families. Most of the variants were frameshift or missense and affected individuals were either homozygous or compound heterozygous in their respective families. We employed GS as a primary test on a subset of 14 families and a secondary tool on 22 families which were unsolved by ES. Although the cumulative detection rate of causal variants by ES and GS is 40% (89/226), GS alone has led to a molecular diagnosis in 7 of 14 families as the primary tool and 5 of 22 families as the secondary test. GS successfully identified variants present in deep intronic or complex regions not detectable by ES.

Atypical ATMs: Broadening the phenotypic spectrum of ATM-associated hereditary cancer.

Heterozygous, loss-of-function germline variants in ATM have been associated with an increased lifetime risk of breast, pancreas, prostate, stomach, ovarian, colorectal, and melanoma cancers. We conducted a retrospective review of thirty-one unrelated patients found to be heterozygous for a germline pathogenic variant in ATM and identified a significant proportion of patients in this cohort with cancers not currently associated with the ATM hereditary cancer syndrome, including carcinomas of the gallbladder, uterus, duodenum, kidney, and lung as well as a vascular sarcoma. A comprehensive review of the literature found 25 relevant studies where 171 individuals with a germline deleterious ATM variant have been diagnosed with the same or similar cancers. The combined data from these studies were then used to estimate the prevalence of germline ATM pathogenic variants in these cancers, which ranged between 0.45% and 2.2%. Analysis of tumor sequencing performed in large cohorts demonstrated that the frequency of deleterious somatic ATM alterations in these atypical cancers equaled or exceeded the alteration frequency in breast cancer and occurred at a significantly higher rate than in other DNA-damage response tumor suppressors, namely BRCA1 and CHEK2. Furthermore, multi-gene analysis of somatic alterations in these atypical cancers demonstrated significant co-occurrence of pathogenic alterations in ATM with BRCA1 and CHEK2, while there was significant mutual exclusivity between pathogenic alterations in ATM and TP53. This indicates that germline ATM pathogenic variants may play a role in cancer initiation and progression in these atypical ATM malignancies, potentially influencing these cancers to be driven toward DNA-damage repair deficiency and away from loss of TP53. As such, these findings provide evidence for broadening of the ATM-cancer susceptibility syndrome phenotype to improve the recognition of affected patients and provide more efficacious, germline-directed therapies.

H4C5 missense variant leads to a neurodevelopmental phenotype overlapping with Angelman syndrome.

Recurrent de novo missense variants in H4 histone genes have recently been associated with a novel neurodevelopmental syndrome that is characterized by intellectual disability and developmental delay as well as more variable findings that include short stature, microcephaly, and facial dysmorphisms. A 4-year-old male with autism, developmental delay, microcephaly, and a happy demeanor underwent evaluation through the Undiagnosed Disease Network. He was clinically suspected to have Angelman syndrome; however, molecular testing was negative. Genome sequencing identified the H4 histone gene variant H4C5 NM_003545.4: c.295T>C, p.Tyr99His, which parental testing confirmed to be de novo. The variant met criteria for a likely pathogenic classification and is one of the seven known disease-causing missense variants in H4C5. A comparison of our proband's findings to the initial description of the H4-associated neurodevelopmental syndrome demonstrates that his phenotype closely matches the spectrum of those reported among the 29 affected individuals. As such, this report corroborates the delineation of neurodevelopmental syndrome caused by de novo missense H4 gene variants. Moreover, it suggests that cases of clinically suspected Angelman syndrome without molecular confirmation should undergo exome or genome sequencing, as novel neurodevelopmental syndromes with phenotypes overlapping with Angelman continue to be discovered.

BCKDK deficiency: a treatable neurodevelopmental disease amenable to newborn screening.

There are few causes of treatable neurodevelopmental diseases described to date. Branched-chain ketoacid dehydrogenase kinase (BCKDK) deficiency causes branched-chain amino acid (BCAA) depletion and is linked to a neurodevelopmental disorder characterized by autism, intellectual disability and microcephaly. We report the largest cohort of patients studied, broadening the phenotypic and genotypic spectrum. Moreover, this is the first study to present newborn screening findings and mid-term clinical outcome. In this cross-sectional study, patients with a diagnosis of BCKDK deficiency were recruited via investigators' practices through a MetabERN initiative. Clinical, biochemical and genetic data were collected. Dried blood spot (DBS) newborn screening (NBS) amino acid profiles were retrieved from collaborating centres and compared to a healthy newborn reference population. Twenty-one patients with BCKDK mutations were included from 13 families. Patients were diagnosed between 8 months and 16 years (mean: 5.8 years, 43% female). At diagnosis, BCAA levels (leucine, valine and isoleucine) were below reference values in plasma and in CSF. All patients had global neurodevelopmental delay; 18/21 had gross motor function (GMF) impairment with GMF III or worse in 5/18, 16/16 intellectual disability, 17/17 language impairment, 12/17 autism spectrum disorder, 9/21 epilepsy, 12/15 clumsiness, 3/21 had sensorineural hearing loss and 4/20 feeding difficulties. No microcephaly was observed at birth, but 17/20 developed microcephaly during follow-up. Regression was reported in six patients. Movement disorder was observed in 3/21 patients: hyperkinetic movements (1), truncal ataxia (1) and dystonia (2). After treatment with a high-protein diet (≥ 2 g/kg/day) and BCAA supplementation (100-250 mg/kg/day), plasma BCAA increased significantly (P < 0.001), motor functions and head circumference stabilized/improved in 13/13 and in 11/15 patients, respectively. Among cases with follow-up data, none of the three patients starting treatment before 2 years of age developed autism at follow-up. The patient with the earliest age of treatment initiation (8 months) showed normal development at 3 years of age. NBS in DBS identified BCAA levels significantly lower than those of the normal population. This work highlights the potential benefits of dietetic treatment, in particular early introduction of BCAA. Therefore, it is of utmost importance to increase awareness about this treatable disease and consider it as a candidate for early detection by NBS programmes.

Deletion of first noncoding exon in ANKRD11 leads to KBG syndrome.

Phenotypic features of KBG syndrome include craniofacial anomalies, short stature, cognitive disability and behavioral findings. The syndrome is caused by heterozygous pathogenic single nucleotide variants and indels in ANKRD11, or a heterozygous deletion of 16q24.3 that includes ANKRD11. We performed genome sequencing on a patient with clinical manifestations of KBG syndrome including distinct craniofacial features as well as a history of mild intellectual disability and attention-deficit hyperactivity disorder. This led to the identification of a 43 kb intragenic deletion of ANKRD11 affecting the first noncoding exon while leaving the coding regions intact. Review of the literature shows that this is the smallest 5' deletion affecting only the noncoding exons of ANKRD11. Real-time polymerase chain reaction demonstrated that the copy number variant was not present in either of the proband's parents, suggesting it occurred de novo. RNA expression analysis demonstrated significantly decreased transcript abundance compared to controls. This provides new evidence for haploinsufficiency as a mechanism of disease in KBG syndrome.