Chromosome 9p terminal deletion in nine Egyptian patients and narrowing of the critical region for trigonocephaly

Whole-Genome Sequencing Reveals Individual and Cohort Level Insights into Chromosome 9p Syndromes

Previous genomic efforts on chromosome 9p deletion and duplication syndromes have utilized low resolution strategies (i.e., karyotypes, chromosome microarrays). We present the first large-scale whole-genome sequencing (WGS) study of 100 individuals from families with 9p-related syndromes including 85 unrelated probands through the 9P-ARCH (Advanced Research in Chromosomal Health: Genomic, Phenotypic, and Functional Aspects of 9p-Related syndromes) research network. We analyzed the genomic architecture of these syndromes, highlighting fundamental features and their commonalities and differences across individuals. This work includes a machine-learning model that predicts 9p deletion syndrome from gene copy number estimates using WGS data. Two Late Replicating Regions (LRR1 [a previously un-named human fragile site], LRR2) were identified that contain most structural variant breakpoints in 9p deletion syndrome pointing to replication-based issues in structural variant formation. Furthermore, we show the utility of using WGS information to obtain a comprehensive understanding of 9p-related variation in an individual with complex structural variation where chromothripsis is the likely mechanism. Genes on 9p were prioritized based on statistical assessment of human genomic variation. Furthermore, through application of spatial transcriptomics to embryonic mouse tissue we examined 9p-gene expression in craniofacial and brain development. Through these strategies, we identified 24 important genes for the majority (83%) of individuals with 9p deletion syndrome including AK3, BRD10, CD274, CDC37L1, DMRT1, DMRT2, DMRT3, DOCK8, GLIS3, JAK2, KANK1, KDM4C, PLPP6, PTPRD, PUM3, RANBP6, RCL1, RFX3, RIC1, SLC1A1, SMARCA2, UHRF2, VLDLR, and ZNG1A. Two genes (AK3, ZNG1A) are involved in mitochondrial function and testing of the mitochondrial genome revealed excess copy number in individuals with 9p deletion syndrome. This study presents the most comprehensive genomic analysis of 9p-related syndromes to date, with plans for further expansion through our 9P-ARCH research network.

Distal 1q Duplication and Distal 9p Deletion: A Follow-Up Case Report and Literature Review on Candidate Genes for 9p Deletion Syndrome

Distal 1q duplication and distal 9p deletion are rare chromosomal aberrations associated with developmental delay and mild to moderate congenital malformations. There are inconsistent findings regarding the critical region for trigonocephaly within 9p deletion syndrome. A recent analysis of the largest 9p- cohort to date, however, delineated two critical regions and emphasized the need for replication. We report on a trigonocephalic child with a de novo 46.09 megabases (Mb) terminal duplication of 1q and a 5.31 Mb terminal deletion in 9p, described as 46,XX,der(9)t(1;9)(q32.1;p24.1). The clinical course was predominantly influenced by the 1q duplication. Trigonocephaly, however, was consistent with 9p deletion syndrome. Our findings support the delineation of [GRCh38] 9:3,418,241-5,341,746 as a critical region for trigonocephaly within 9p deletion syndrome. We propose that haploinsufficiency of RFX3, along with complex gene interactions, contributes to the mechanism for disease.

Generation of Dual-Color FISH probes targeting 9p21, Xp21, and 17p13.1 loci as diagnostic markers for some genetic disorders and cancer in Egypt

INTRODUCTION

The fluorescence in situ hybridization (FISH) is a very important technique, as it can diagnose many genetic disorders and cancers. Molecular cytogenetic analysis (FISH) can diagnose numerical chromosome aberrations, sex chromosomes anomalies, and many genetic disorders.

AIM

With the limited number of commercially available probes that do not cover all research needs and the high prices of the commercial probes, our goal is to apply recent technologies to produce FISH probes that can accurately and sensitively diagnose genetic diseases and cancer in Egypt and establishing the inhouse production of different FISH probes. We intend to adhere to the published guidelines and validation procedures to ensure the production of accurate FISH probes for clinical diagnosis.

METHODS

We used specific DNA segments extracted from BAC clones, and we performed nick translation to label the segment with fluorescence labeled dye. The second method involved the use of specific primers for the centromere of certain chromosomes and using PCR technique for amplification and labeling. The probes were tested on metaphase and interphase cells derived from cultured human peripheral blood samples. We followed standard guidelines to test the adequacy of probe slide hybridization, proper probe localization, probe sensitivity and specificity, probe reproducibility, cut-off values, and overall probe validation.

RESULTS

In this research, we presented the generation of three dual-color probes, each probe has a control locus. We offered three dual-color probes targeted 9p21, Xp21 and 17p13.1 loci. chromosome 9p21probe for diagnosis of structural abnormalities in chromosome 9, the Xp21 to test for structural abnormalities of chromosome X, and the 17p13.1 for TP53 gene to detect the loss of p53. We also produced probes for Down syndrome specific region, Rb gene and centromeres for chromosomes X, 17, and 18.

CONCLUSION

The produced probes are specific and sensitive and can be produced at the commercial level in the laboratory. The production of FISH probes in Egypt can be used as a powerful diagnostic marker for genetic disorders and cancers and our work can be consider as a base to start national project to produce our needs of FISH probes.

Craniosynostosis in Africa: Insights from 8 Countries-A Systematic Review and Meta-Analysis

OBJECTIVE

Craniosynostosis is a congenital skull deformity that impacts development and quality of life of children if left untreated. This study aimed to evaluate literature regarding presentation, treatment, and outcomes of craniosynostosis in Africa.

METHODS

A systematic review of the literature using PubMed/MEDLINE, Scopus, Web of Science, and Google Scholar databases was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

RESULTS

Fourteen retrospective/prospective studies with 620 patients and 14 case reports involving 27 cases (8 countries) were included. In 12 articles, 56.6% of patients (317/560) were males, with a mean age of 2.4 years (confidence interval [CI]: 1.1-3.7). Abnormal head shape was the most reported presentation in 77.8% of cases (332/427, 8 articles). Syndromic craniosynostosis was seen in 25.2% (CI: 13.7%-36.6%). Common phenotypes were trigonocephaly in 31.5% (CI: 3.6%-59.4%), anterior plagiocephaly in 23.2% (CI: 5.1%-41.3%), and scaphocephaly in 22.1% (CI: 13.5%-30.8%). Five hundred seventy eight patients, 99.5% (CI: 99.0%-100.0%), underwent surgical treatment. Vault remodeling was performed in 72.9% patients (CI: 47.4%-98.6%). Postoperative complications included cerebrospinal fluid leaks 5.4% (CI: 0.0%-11.6%) and surgical site infections 4.5% (CI: 0.0%-10.8%). Follow-up ranged between 0.2 and 40.9 months; 95.6% of cases (CI: 90.1%-100.0%) exhibited improved deformity and neurological deficits at last follow-up. The mortality rate was 3.1% (CI: 0.0%-6.9%, 2 articles).

CONCLUSIONS

Few studies on craniosynostosis in Africa highlight the need for more research. Treatment with open techniques yields few complications and a low mortality rate. Early diagnosis and collaborative data reporting will enhance understanding of its burden and variations across Africa.

Using a new analytic approach for genotyping and phenotyping chromosome 9p deletion syndrome

Using a new analytic method ("unique non-overlapping region" (UNOR) analysis), we characterized the genotypes and phenotypes of a large cohort of individuals diagnosed with chromosome 9p deletion syndrome (9PMS) and defined critical genomic regions. We extracted phenotypic information from 48 individuals with 9PMS from medical records and used a guided interview with caregivers to clarify ambiguities. Using high-resolution whole-genome sequencing for breakpoint definition, we aligned deletions and drew virtual breakpoints to obtain UNORs associated with phenotypic characteristics. We next extracted genotype and phenotype data for 57 individuals identified from a systematic review of the 9PMS literature and analyzed these as above. Common phenotypic features included developmental delay/intellectual disability, dysmorphic features, hypotonia, genital defects in XY individuals, psychiatric diagnoses, chronic constipation, atopic disease, vision problems, autism spectrum disorder, gastroesophageal reflux disease, trigonocephaly, congenital heart disease, and neonatal hypoglycemia. Our approach confirmed previous literature reports of an association of FREM1 with trigonocephaly and suggested a possible modifier element for this phenotype. In conclusion, the UNOR approach delineated phenotypic characteristics for 9PMS and confirmed the critical role of FREM1 and a possible long-distance regulatory element in pathogenesis of trigonocephaly that will need to be replicated in future studies.

New candidate region for mirror hand movements: two patients with terminal 9p deletion and 20p duplication

The 9p deletion syndrome, which was defined in a detailed way in the previous studies, was characterized by various clinical features such as psychomotor retardation, dysmorphic features and genital anomalies. In contrast to 9p deletion syndrome, 20p duplication was rarely reported in the literature with only a few case reports. Regarding the combination of 9p deletion syndrome and 20p duplication, we found that it was reported in only four patients. In the current study, we aimed to investigate a rare chromosomal rearrangement, partial monosomy 9p and trisomy 20p which was observed in two patients with mirror hand movements. The mirror hand movements was influenced by the combination of genetic and environmental factors. While some cases have been associated with mutations in the DCC, NTN1, RAD51, and DNAL4, there were many cases where the genetic basis of mirror hand movements remained unexplained. There was no alteration detected in genes that were previously known as a cause of mirror hand movement in our patients. This new finding could potentially be attributed to the dosage effect of genes within the 9p deletion or 20p duplication regions or to the genes disrupted within the breakpoint region. Future research focusing on the genes within this genomic locus may hold the potential to uncover novel etiologic reasons for mirror hand movements.

From karyotypes to precision genomics in 9p deletion and duplication syndromes

While 9p deletion and duplication syndromes have been studied for several years, small sample sizes and minimal high-resolution data have limited a comprehensive delineation of genotypic and phenotypic characteristics. In this study, we examined genetic data from 719 individuals in the worldwide 9p Network Cohort: a cohort seven to nine times larger than any previous study of 9p. Most breakpoints occur in bands 9p22 and 9p24, accounting for 35% and 38% of all breakpoints, respectively. Bands 9p11 and 9p12 have the fewest breakpoints, with each accounting for 0.6% of all breakpoints. The most common phenotype in 9p deletion and duplication syndromes is developmental delay, and we identified eight known neurodevelopmental disorder genes in 9p22 and 9p24. Since it has been previously reported that some individuals have a secondary structural variant related to the 9p variant, we examined our cohort for these variants and found 97 events. The top secondary variant involved 9q in 14 individuals (1.9%), including ring chromosomes and inversions. We identified a gender bias with significant enrichment for females (p = 0.0006) that may arise from a sex reversal in some individuals with 9p deletions. Genes on 9p were characterized regarding function, constraint metrics, and protein-protein interactions, resulting in a prioritized set of genes for further study. Finally, we achieved precision genomics in one child with a complex 9p structural variation using modern genomic technologies, demonstrating that long-read sequencing will be integral for some cases. Our study is the largest ever on 9p-related syndromes and provides key insights into genetic factors involved in these syndromes.

Chromosome 9p terminal deletion in nine Egyptian patients and narrowing of the critical region for trigonocephaly

Background

This study aimed to delineate the clinical phenotype of patients with 9p deletions, pinpoint the chromosomal breakpoints, and identify the critical region for trigonocephaly, which is a frequent finding in 9p terminal deletion.

Methods

We investigated a cohort of nine patients with chromosome 9p terminal deletions who all displayed developmental delay, intellectual disability, hypotonia, and dysmorphic features. Of them, eight had trigonocephaly, seven had brain anomalies, seven had autistic manifestations, seven had fair hair, and six had a congenital heart defect (CHD).

Results

Karyotyping revealed 9p terminal deletion in all patients, and patients 8 and 9 had additional duplication of other chromosomal segments. We used six bacterial artificial chromosome (BAC) clones that could identify the breakpoints at 17–20 Mb from the 9p terminus. Array CGH identified the precise extent of the deletion in six patients; the deleted regions ranged from 16 to 18.8 Mb in four patients, patient 8 had an 11.58 Mb deletion and patient 9 had a 2.3 Mb deletion.

Conclusion

The gene deletion in the 9p24 region was insufficient to cause ambiguous genitalia because six of the nine patients had normal genitalia. We suggest that the critical region for trigonocephaly lies between 11,575 and 11,587 Mb from the chromosome 9p terminus. To the best of our knowledge, this is the minimal critical region reported for trigonocephaly in 9p deletion syndrome, and it warrants further delineation.