Combining RSPH9 founder mutation screening and next-generation sequencing analysis is efficient for primary ciliary dyskinesia diagnosis in Saudi patients.

Primary ciliary dyskinesia (PCD) is a clinically and genetically heterogeneous ciliopathy. Dysfunction of motile respiratory and nodal cilia results in sinopulmonary symptoms associated with laterality defects (LD) found in half of the patients. The molecular basis of the disease is insufficiently investigated in patients originating from the Arabian Peninsula. In a group of 16 unrelated Saudi patients clinically suspected of PCD and among whom only 5 (31%) had LD, we first screened by PCR-RFLP two founder mutations, RSPH9 c.804_806del and CCDC39 c.2190del previously identified in patients from the Arabian Peninsula and Tunisia, respectively. When negative, targeted panel or whole-exome sequencing was performed. Three patients were homozygous for the mutation in RSPH9, which encodes an axonemal protein that is absent from nodal cilia. None of the patients carried the CCDC39 founder mutation frequent in Tunisia. NGS analysis showed that nine patients had homozygous mutations in PCD genes. In total, sequential RFLP and NGS analysis solved 75% (12/16) of cases and identified ten distinct mutations, among which six are novel, in nine different genes. These results, which highlight the genetic heterogeneity of PCD in Saudi Arabia, show that the RSPH9 c.804_806del mutation is a prevalent mutation among Saudi patients, whereas the CCDC39 c.2190del ancestral allele is most likely related to the Berber population. This study shows that RSPH9 founder mutation first-line screening and NGS analysis is efficient for the genetic exploration of PCD in Saudi patients. The RSPH9 founder mutation accounts for the low rate of LD among Saudi patients.

Primary ciliary dyskinesia gene contribution in Tunisia: Identification of a major Mediterranean allele.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disease of motile cilia. Even though PCD is widely studied, North-African patients have been rarely explored. In this study, we aim at confirming the clinical diagnosis and explore the genetic spectrum of PCD in a cohort of Tunisian patients. Forty clinically diagnosed patients with PCD belonging to 34 families were recruited from Tunisian pediatric departments. In each proband, targeted capture PCD panel sequencing of the 40 PCD genes was performed. PCD panel sequencing identified bi-allelic mutations in 82% of the families in eight PCD genes. Remarkably, 23.5% of patients carried the same c.2190del CCDC39 mutation. Single nucleotide polymorphism profiling in six unrelated patients carrying this mutation has revealed a founder effect in North-African patients. This mutation is estimated to date back at least 1,400-1,750 years ago. The identification of this major allele allowed us to suggest a cost-effective genetic diagnostic strategy in North-African patients with PCD.

GATA2 gene analysis in several forms of hematological malignancies including familial aggregations.

The genetic predisposition to familial hematological malignancies has been previously reported highlighting inherited gene mutations. Several genes have been reported but genetic basis remains not well defined. In this study, we extended our investigation to a potential candidate GATA2 gene which was analyzed by direct sequencing in 119 cases including familial aggregations with a variety of hematological malignancies and sporadic acute leukemia belonging to Tunisian and French populations. We reported a deleterious p.Arg396Gln GATA2 mutation in one patient diagnosed with both sporadic acute myeloid leukemia (AML) and breast cancer. We also reported several GATA2 variations in familial cases. The absence of deleterious mutations in this large cohort of familial aggregations of hematological malignancies may strengthen the hypothesis that GATA2 mutations are an important predisposing factor, although as a secondary genetic event, required for the development of overt malignant disease.

High Nasal Nitric Oxide, Cilia Analyses, and Genotypes in a Retrospective Cohort of Children with Primary Ciliary Dyskinesia.

Rationale: Although children with primary ciliary dyskinesia (PCD) typically have low nasal nitric oxide (nNO), some children with indisputable PCD may have unexplained high nNO concentrations. Objectives: To look for relationships between nNO measures and genetic findings (and cilia motility or ultrastructure when available) in children with PCD with known genotypes. Methods: We retrospectively studied 73 children with PCD (median age, 9.5 [range, 2.1-18.2] yr). nNO was the mean value of a plateau reached while the velum was closed (nNO-VC; threshold, 77 nl ⋅ min-1) or was calculated as the average of five peaks obtained during tidal breathing (threshold, 40 nl ⋅ min-1). Ciliary beat was classified as either motile (including dyskinetic pattern) or immotile, depending on whether motility was present or absent in all cilia, or as a mixture of motile and immotile cilia. Genotypes were classified as pathogenic mutations in genes known to be associated with high nNO (mild genotype), biallelic truncating mutations in other genes (severe mutations), or putative hypomorphic pathogenic mutations (missense, single amino acid deletion, or moderate splicing mutations) in at least one allele believed to be possibly associated with residual production of a functional protein. Results: nNO was above the discriminant threshold in 16 of 73 (21.9%) children (11 nNO-VC and 5 nNO during tidal breathing). High nNO was less frequent in children with severe mutations (2 of 42) than in those with mild genotypes (7 of 10) or at least one hypomorphic mutation (7 of 21) (P < 0.0001). Median (interquartile range) nNO-VC values (n = 60) were significantly different in the three genotype groups: severe mutations, 18 (10-26) nl ⋅ min-1 (n = 36); possible residual functional protein production (putative hypomorphic mutations), 23 (16-68) nl ⋅ min-1 (n = 17); and mild genotypes, 139 (57-216) nl ⋅ min-1 (n = 7) (P = 0.0002). The higher the cilia motility, the higher the nNO-VC (16 [10-23], 23 [17-56], and 78 [45-93] nl ⋅ min-1 in patients with immotile, dyskinetic motile and immotile, and dyskinetic motile cilia, respectively; P < 0.0001), while nNO values were scattered across different ultrastructure defects (P = 0.07). Conclusions: In children with PCD, high nNO values were linked not only to specific genes but also to potentially hypomorphic mutations in other genes (with possible functional protein production). nNO values increased with the proportion of motile cilia.

An overview of genetic predisposition to familial hematological malignancies.

Genetic predisposition has been always noted in the context of familial hematological malignancies. Epidemiological studies have provided evidence consisting of an increased risk to develop blood cancer in relatives diagnosed with the same pathology and characterized by early age at diagnosis and higher severity compared to sporadic forms. With the emergence of new genomic testing approaches, the prevalence of familial aggregations of hematological malignancies seems to be under estimated. The heterogeneity of clinical features explains the wide number of genes' mutations reported to date and the variable penetrance of variants. Nevertheless, the genetic basis of familial hematological malignancies is still not well understood. Identifying the genetic background in familial aggregations provides a valuable tool for prognostic evaluation, personalized treatment and better genetic counseling in high-risk families. Herein, we provide an overview of genes reported in the last few years in association to hematological malignancies including familial form of Hodgkin Lymphoma, Non-Hodgkin Lymphoma, Chronic Lymphocytic Leukemia, acute Myeloid Leukemia and acute Lymphoblastic Leukemia.

Mutational analysis of apoptotic genes in familial aggregation of hematological malignancies.

INTRODUCTION: Apoptosis deregulation have been associated to tumorigenesis process and was highlighted as a prominent hallmark of cancer. Several mutations have been reported in several forms of Blood cancer. However, it has never been investigated in familial aggregations of hematological malignancies. METHODS: In this study, we performed a mutational analysis by sequencing the entire coding regions in four key apoptotic genes FAS, FASLG, CASP8 and CASP10 in 92 independent families belonging to French and Tunisian populations and diagnosed with several forms of familial hematological malignancies. RESULTS: We report 15 genetic variations among which 7 were previously reported in several form of cancers and have a potential effect on gene expression. Particularly, the CASP8 variants p.Asp302His and p.Lys337Lys were detected in 15% and 10% of our group of patients respectively and were previously reported in association to breast cancer and to breast cancer susceptibility. DISCUSSION: In this study, we do not report the underlining deleterious mutations in familial hematological malignancies, but we describe some variants with potential risk of developing blood cancer. To gain further insights on the association between apoptosis pathway deregulation and familial hematological malignancies, more apoptotic genes should be investigated.

A novel DNAH5 variant in a Tunisian patient with primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous hereditary disease caused by the structural abnormalities and dysfunction of motile cilia. The DNAH5 is the most frequently mutated gene in PCD patients and hot spot exons were reported in this gene. Here, we aim to screen mutations in a set of five hot spot exons of DNAH5 gene in a cohort of 10 clinically diagnosed Tunisian PCD patients using an optimized polymerase chain reaction-single-strand conformational polymorphism screening technique. Only one patient harboured a novel heterozygous variant in exon 63 (c.10767A>G), which was inherited from his father. This variant activates a cryptic splicing site. No deleterious mutation has been identified while screening the exons of the remaining patients. Our results show that the reported hot spot exons of DNAH5 gene are not mutated in Tunisian PCD patients. This is probably due to the differences of ethnical background of the previously reported patients. Further investigations should be performed to identify the mutations underlying PCD in this group of patients.

ARLTS1, potential candidate gene in familial aggregation of hematological malignancies.

INTRODUCTION: Genetic predisposition to familial hematological malignancies was previously described through several epidemiological analyses, but the genetic basis remains unclear. The tumor-suppressor ARLTS1 gene was previously described in sporadic hematological malignancies and familial cancer context. METHODS: In this study, we sequence the ARLTS1 gene in 100 patients belonging to 88 independent Tunisian and French families. RESULTS: After gene sequencing, we report 8 genetic variations, most of which were previously reported in several cancer forms. The most common variants were W149X and C148R and were previously associated to B-cell chronic lymphocytic leukemia and to high-risk of familial breast cancer. CONCLUSIONS: These results emphasize the fact that ARLTS1 gene mutations can be considered as a potential predisposing factor in familial hematological malignancies and other several cancer forms.