Pedigree-Based Gene Mapping Supports Previous Loci and Reveals Novel Suggestive Loci in Specific Language Impairment

Whole exome sequencing identifies ABHD14A and MRNIP as novel candidate genes for developmental language disorder

Developmental language disorder (DLD) is a neurodevelopmental disorder involving impaired language abilities. Its genetic etiology is heterogeneous, involving rare variations in multiple susceptibility loci. However, family-based studies on gene mutations are scarce. We performed whole-exome sequencing (WES) of a first-time-described Tunisian-family with DLD. Analyses of segregation patterns with stringent filtering of the exome data identified disease-causing compound heterozygous variants. In the MRNIP gene, two variants were detected including a synonymous low-frequency variant c.345G > C and a nonsense rare variant c.112G > A predicted pathogenic. In the ABHD14A gene, four variants were identified including a rare missense variant c.689T > G and three splice-site variants c.70-8C > T, c.282-25A > T and c.282-10G > C with low-frequency MAF < 5%. Complementary analyses showed that these variants are predicted pathogenic and the missense variant Leu230Arg significantly affects the stability and structure modelling of the ABHD14A protein. Biological functions and interconnections analyses predicted the potential roles of ABHD14A and MRNIP in neuronal development pathways. These results suggest ABHD14A and MRNIP, as putative candidate genes for DLD susceptibility. Our findings reveal the involvement of novel candidate genes in the genetic etiology of DLD and explore the potential future utility of WES in the diagnosis of such complex disorders.

Genome-Wide Mapping of Consanguineous Families Confirms Previously Implicated Gene Loci and Suggests New Loci in Specific Language Impairment (SLI)

Specific language impairment (SLI) is a developmental disorder with substantial genetic contributions. A genome-wide linkage analysis and homozygosity mapping were performed in five consanguineous families from Pakistan. The highest LOD scores of 2.49 at 12p11.22-q11.21 in family PKSLI-31 and 1.92 at 6p in family PKSLI-20 were observed. Homozygosity mapping showed a loss of heterozygosity on 1q25.3-q32.2 and 2q36.3-q37.3 in PKSLI-20. A loss of heterozygosity mapped, in PKSLI-31 and PKSLI-34 flanks, NFXL1 and CNTNAP2, which are genes previously identified in SLI. Our findings report novel SLI loci and corroborate previously reported SLI loci, indicating the utility of a family-based approach.

Whole Genome Analysis in Consanguineous Families Reveals New Loci for Speech Sound Disorder (SSD)

Speech is the most common means of communication in humans. Any defect in accurate speech production ability results in the development of speech sound disorder (SSD), a condition that can significantly impair an individual's academic performance, social interactions, and relationships with peers and adults. This study investigated the genetic basis of SSD in three Pakistani families. We performed family-based genome-wide parametric linkage analysis and homozygosity mapping in three consanguineous families with SSD from the Punjab province of Pakistan. The Test for Assessment of Articulation and Phonology in Urdu (TAAPU) was used to analyze the speech articulation data and determine the Percentage Correct Consonants (PCC) score. The PCC score defined the affected and unaffected individuals in each family. Parametric linkage analysis revealed a linkage to chromosome 5 (5q21.3-5q23.1) with a significant logarithm of the odds (LOD) score of 3.13 in a Pakistani family with specific language impairment-97 (PKSLI-97) under an autosomal recessive mode of inheritance. The other two families showed a suggestive linkage at 6p22.1, 14q12, and 16q12.1 under the recessive mode of inheritance. Interestingly, homozygosity mapping showed a loss of heterozygosity in the linkage region at 5q15-5q23.1, shared among seven affected (mostly in the younger generation) and one unaffected individual of PKSLI-97. Our analysis identified the 6p22 locus previously implicated in dyslexia, childhood apraxia of speech (CAS), and language impairment, confirming the role of KIAA0319 and DCDC2 in this locus. These findings provide statistical evidence for the genomic regions associated with articulation disorder and offer future opportunities to further the role of genes in speech production.

Innovative Family-Based Genetically Informed Series of Analyses of Whole-Exome Data Supports Likely Inheritance for Grammar in Children with Specific Language Impairment

Individuals with specific language impairment (SLI) struggle with language acquisition despite average non-verbal intelligence and otherwise typical development. One SLI account focuses on grammar acquisition delay. The current study aimed to detect novel rare genetic variants associated with performance on a grammar assessment, the Test of Early Grammatical Impairment (TEGI), in English-speaking children. The TEGI was selected due to its sensitivity and specificity, consistently high heritability estimates, and its absence from all but one molecular genetic study. We performed whole exome sequencing (WES) in eight families with SLI (n = 74 total) and follow-up Sanger sequencing in additional unrelated probands (n = 146). We prioritized rare exonic variants shared by individuals with low TEGI performance (n = 34) from at least two families under two filtering workflows: (1) novel and (2) previously reported candidate genes. Candidate variants were observed on six new genes (PDHA2, PCDHB3, FURIN, NOL6, IQGAP3, and BAHCC1), and two genes previously reported for overall language ability (GLI3 and FLNB). We specifically suggest PCDHB3, a protocadherin gene, and NOL6 are critical for ribosome synthesis, as they are important targets of SLI investigation. The proposed SLI candidate genes associated with TEGI performance emphasize the utility of precise phenotyping and family-based genetic study.

Genome-wide analysis of runs of homozygosity in Pakistani controls with no history of speech or language-related developmental phenotypes

BACKGROUND

Runs of homozygosity (ROHs) analysis of controls provide a convenient resource to minimize the association of false positive results of disease-associated ROHs and genetic variants for simple and complex disorders in individuals from the same population. Evidence for the value of ROHs to speech or language-related traits is restricted due to the absence of population-matched behaviourally defined controls and limited family-based studies.

AIM

This study aims to identify common ROHs in the Pakistani population, focussing on the total length and frequency of ROHs of variable sizes, shared ROHs, and their genomic distribution.

SUBJECTS AND METHODS

We performed homozygosity analysis (in PLINK) of 86 individuals (39 males, 47 females) with no history of speech or language-related phenotypes (controls) who had been genotyped with the Illumina Infinium QC Array-24.

RESULTS

ROHs of 1-<4 megabases (Mb) were frequent in unrelated individuals. We observed ROHs over 20 Mb among six individuals. Over 30 percent of the identified ROHs were shared among several individuals, indicating consanguinity's effect on the Pakistani population.

CONCLUSION

Our findings serve as a foundation for family-based genetic studies of consanguineous families with speech or language-related disorders to ultimately narrow the homozygosity regions of interest to identify pathogenic variants.

Contemporary Theories of Stuttering Development

The article presents a theoretical analysis of contemporary models of persistent stuttering development in children and adults at the current period of development of science. The accumulated amount of scientific knowledge suggests that stuttering has a neurological basis: it is associated with disorders in the structure and function of the brain. On this basis, there have been emerged models of stuttering that link the cause of a speech disorder with an unstable speech motor system. Theories and models of stuttering based on cognitive and language processing are likely to be useful in that they have explanatory power in relation to the mechanisms that play an important role in the production of key symptoms of stuttering. Considering that stuttering is a complex disorder, the logical result of this was the proposal of multifactorial models of impaired speech fluency. The presented overview may be useful to psychiatrists, clinical psychologists, speech therapists, teachers, and practitioners interacting with children and adults with stuttering and other speech fluency disorders.

Family-Based Whole-Exome Analysis of Specific Language Impairment (SLI) Identifies Rare Variants in BUD13, a Component of the Retention and Splicing (RES) Complex

Specific language impairment (SLI) is a common neurodevelopmental disorder (NDD) that displays high heritability estimates. Genetic studies have identified several loci, but the molecular basis of SLI remains unclear. With the aim to better understand the genetic architecture of SLI, we performed whole-exome sequencing (WES) in a single family (ID: 489; n = 11). We identified co-segregating rare variants in three new genes: BUD13, APLP2, and NDRG2. To determine the significance of these genes in SLI, we Sanger sequenced all coding regions of each gene in unrelated individuals with SLI (n = 175). We observed 13 additional rare variants in 18 unrelated individuals. Variants in BUD13 reached genome-wide significance (p-value < 0.01) upon comparison with similar variants in the 1000 Genomes Project, providing gene level evidence that BUD13 is involved in SLI. Additionally, five BUD13 variants showed cohesive variant level evidence of likely pathogenicity. Bud13 is a component of the retention and splicing (RES) complex. Additional supportive evidence from studies of an animal model (loss-of-function mutations in BUD13 caused a profound neural phenotype) and individuals with an NDD phenotype (carrying a CNV spanning BUD13), indicates BUD13 could be a target for investigation of the neural basis of language.

Study of rare genetic variants in TM4SF20, NFXL1, CNTNAP2, and ATP2C2 in Pakistani probands and families with language impairment

Language impairment (LI) is highly heritable and aggregates in families. Genetic investigation of LI has revealed many chromosomal regions and genes of interest, though very few studies have focused on rare variant analysis in non-English speaking or non-European samples. We selected four candidate genes (TM4SF20, NFXL1, CNTNAP2 and ATP2C2) strongly suggested for specific language impairment (SLI), a subtype of LI, and investigated rare protein coding variants through Sanger sequencing of probands with LI ascertained from Pakistan. The probands and their family members completed a speech and language family history questionnaire and a vocabulary measure, the Peabody Picture Vocabulary Test-fourth edition (PPVT-4), translated to Urdu, the national language of Pakistan. Our study aimed to determine the significance of rare variants in these SLI candidate genes through segregation analysis in a novel population with a high rate of consanguinity. In total, we identified 16 rare variants (according to the rare MAF in the global population in gnomAD v2.1.1 database exomes), including eight variants with a MAF <0.5 % in the South Asian population. Most of the identified rare variants aggregated in proband's families, one rare variant (c.*9T>C in CNTNAP2) co-segregated in a small family (PKSLI-64) and another (c.2465C>T in ATP2C2) co-segregated in the proband branch (PKSLI-27). The lack of complete co-segregation of most of the identified rare variants indicates that while these genes could be involved in overall risk for LI, other genes are likely involved in LI in this population. Future investigation of these consanguineous families has the potential to expand our understanding of gene function related to language acquisition and impairment.

Developing, Implementing, and Learning from a Student-Led Initiative to Support Minority Students in Communication Sciences and Disorders

PURPOSE

The Student Equity and Inclusion Workgroup is a student-led initiative at the University of Kansas that aims to advance equity and inclusion. Within this structure, the workgroup is entirely student-led and independent of any institutional initiatives. It has developed three themes - recognizing minority student leadership, ensuring equitable access to opportunities, and meaningfully supporting students - and used those themes to develop comprehensive programming in the way of research, institutional advocacy, mentorship, and fellowship. Research initiatives included creating research opportunities for minority students by developing independent research projects. Institutional advocacy initiatives focused on policy change and developing a uniquely situated network of allies at and beyond the university. Mentorship centered student-to-student transmission of knowledge, skills, and support. Fellowship entailed creating opportunities for community-building and recognition of minority student excellence.

CONCLUSIONS

Student-led initiatives such as those of the workgroup may be an effective way of supporting minority students in CSD. Institutions endeavoring to advance equity and inclusion should consider empowering students through facilitation of self-directed development, using institutional supports to support minority students on their terms, and recognizing students as capable partners in rethinking equity and inclusion.

A rare missense variant in the ATP2C2 gene is associated with language impairment and related measures

At least 5% of children present unexpected difficulties in expressing and understanding spoken language. This condition is highly heritable and often co-occurs with other neurodevelopmental disorders such as dyslexia and ADHD. Through an exome sequencing analysis, we identified a rare missense variant (chr16:84405221, GRCh38.p12) in the ATP2C2 gene. ATP2C2 was implicated in language disorders by linkage and association studies, and exactly the same variant was reported previously in a different exome sequencing study for language impairment (LI). We followed up this finding by genotyping the mutation in cohorts selected for LI and comorbid disorders. We found that the variant had a higher frequency in LI cases (1.8%, N = 360) compared with cohorts selected for dyslexia (0.8%, N = 520) and ADHD (0.7%, N = 150), which presented frequencies comparable to reference databases (0.9%, N = 24 046 gnomAD controls). Additionally, we observed that carriers of the rare variant identified from a general population cohort (N = 42, ALSPAC cohort) presented, as a group, lower scores on a range of reading and language-related measures compared to controls (N = 1825; minimum P = 0.002 for non-word reading). ATP2C2 encodes for an ATPase (SPCA2) that transports calcium and manganese ions into the Golgi lumen. Our functional characterization suggested that the rare variant influences the ATPase activity of SPCA2. Thus, our results further support the role of ATP2C2 locus in language-related phenotypes and pinpoint the possible effects of a specific rare variant at molecular level.