@article {521, title = {A comprehensive clinical and genetic study in 127 patients with ID in Kinshasa, DR Congo.}, journal = {Am J Med Genet A}, volume = {176}, year = {2018}, month = {2018 09}, pages = {1897-1909}, abstract = {

Pathogenic variants account for 4 to 41\% of patients with intellectual disability (ID) or developmental delay (DD). In Sub-Saharan Africa, the prevalence of ID is thought to be higher, but data in Central Africa are limited to some case reports. In addition, clinical descriptions of some syndromes are not available for this population. This study aimed at providing an estimate for the fraction of ID/DD for which an underlying etiological genetic cause may be elucidated and provide insights into their clinical presentation in special institutions in a Central African country. A total of 127 patients (33 females and 94 males, mean age 10.03 {\textpm} 4.68 years), were recruited from six institutions across Kinshasa. A clinical diagnosis was achieved in 44 but molecular confirmation was achieved in 21 of the 22 patients with expected genetic defect (95\% clinical sensitivity). Identified diseases included Down syndrome (15\%), submicroscopic copy number variants (9\%), aminoacylase deficiency (0.8\%), Partington syndrome in one patient (0.8\%) and his similarly affected brother, X-linked syndromic Mental Retardation type 33 (0.8\%), and two conditions without clear underlying molecular genetic etiologies (Oculo-Auriculo-Vertebral and Amniotic Bands Sequence). We have shown that genetic etiologies, similar to those reported in Caucasian subjects, are a common etiologic cause of ID in African patients from Africa. We have confirmed the diagnostic utility of clinical characterization prior to genetic testing. Finally, our clinical descriptions provide insights into the presentation of these genetic diseases in African patients.

}, issn = {1552-4833}, doi = {10.1002/ajmg.a.40382}, author = {Lumaka, Aim{\'e} and Race, Valerie and Peeters, Hilde and Corveleyn, Anniek and Coban-Akdemir, Zeynep and Jhangiani, Shalini N and Song, Xiaofei and Mubungu, Gerrye and Posey, Jennifer and Lupski, James R and Vermeesch, Joris R and Lukusa, Prosper and Devriendt, Koenraad} } @article {59, title = {Identification of Intellectual Disability Genes in Female Patients with a Skewed X-Inactivation Pattern.}, journal = {Hum Mutat}, volume = {37}, year = {2016}, month = {2016 08}, pages = {804-11}, abstract = {

Intellectual disability (ID) is a heterogeneous disorder with an unknown molecular etiology in many cases. Previously, X-linked ID (XLID) studies focused on males because of the hemizygous state of their X chromosome. Carrier females are generally unaffected because of the presence of a second normal allele, or inactivation of the mutant X chromosome in most of their cells (skewing). However, in female ID patients, we hypothesized that the presence of skewing of X-inactivation would be an indicator for an X chromosomal ID cause. We analyzed the X-inactivation patterns of 288 females with ID, and found that 22 (7.6\%) had extreme skewing (>90\%), which is significantly higher than observed in the general population (3.6\%; P~=~0.029). Whole-exome sequencing of 19 females with extreme skewing revealed causal variants in six females in the XLID genes DDX3X, NHS, WDR45, MECP2, and SMC1A. Interestingly, variants in genes escaping X-inactivation presumably cause both XLID and skewing of X-inactivation in three of these patients. Moreover, variants likely accounting for skewing only were detected in MED12, HDAC8, and TAF9B. All tested candidate causative variants were de novo events. Hence, extreme skewing is a good indicator for the presence of X-linked variants in female patients.

}, keywords = {Carrier Proteins, Cell Cycle Proteins, Chromosomal Proteins, Non-Histone, DEAD-box RNA Helicases, Exome, Female, Genetic Variation, Humans, Intellectual Disability, Methyl-CpG-Binding Protein 2, Nuclear Proteins, Sequence Analysis, DNA, X Chromosome Inactivation}, issn = {1098-1004}, doi = {10.1002/humu.23012}, author = {Fieremans, Nathalie and Van Esch, Hilde and Holvoet, Maureen and Van Goethem, Gert and Devriendt, Koenraad and Rosello, Monica and Mayo, Sonia and Martinez, Francisco and Jhangiani, Shalini and Muzny, Donna M and Gibbs, Richard A and Lupski, James R and Vermeesch, Joris R and Marynen, Peter and Froyen, Guy} } @article {229, title = {Parental somatic mosaicism is underrecognized and influences recurrence risk of genomic disorders.}, journal = {Am J Hum Genet}, volume = {95}, year = {2014}, month = {2014 Aug 07}, pages = {173-82}, abstract = {

New human mutations are thought to originate in germ cells, thus making a recurrence of the same mutation in a sibling exceedingly rare. However, increasing sensitivity of genomic technologies has anecdotally revealed mosaicism for mutations in somatic tissues of apparently healthy parents. Such somatically mosaic parents might also have germline mosaicism that can potentially cause unexpected intergenerational recurrences. Here, we show that somatic mosaicism for transmitted mutations among parents of children with simplex genetic disease is more common than currently appreciated. Using the sensitivity of individual-specific breakpoint PCR, we prospectively screened 100 families with children affected by genomic disorders due to rare deletion copy-number variants (CNVs) determined to be de novo by clinical analysis of parental DNA. Surprisingly, we identified four cases of low-level somatic mosaicism for the transmitted CNV in DNA isolated from parental blood. Integrated probabilistic modeling of gametogenesis developed in response to our observations predicts that mutations in parental blood increase recurrence risk substantially more than parental mutations confined to the germline. Moreover, despite the fact that maternally transmitted mutations are the minority of alleles, our model suggests that sexual dimorphisms in gametogenesis result in a greater proportion of somatically mosaic transmitting mothers who are thus at increased risk of recurrence. Therefore, somatic mosaicism together with sexual differences in gametogenesis might explain a considerable fraction of unexpected recurrences of X-linked recessive disease. Overall, our results underscore an important role for somatic mosaicism and mitotic replicative mutational mechanisms in transmission genetics.

}, keywords = {Cell Division, DNA Copy Number Variations, Female, Gametogenesis, Genetic Diseases, Inborn, Genomics, Germ Cells, Germ-Line Mutation, Humans, Male, Models, Genetic, Mosaicism, Mutation, Pedigree, Prospective Studies, Recurrence, Risk, Sex Characteristics, Smith-Magenis Syndrome}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2014.07.003}, author = {Campbell, Ian M and Yuan, Bo and Robberecht, Caroline and Pfundt, Rolph and Szafranski, Przemyslaw and McEntagart, Meriel E and Nagamani, Sandesh C S and Erez, Ayelet and Bartnik, Magdalena and Wi{\'s}niowiecka-Kowalnik, Barbara and Plunkett, Katie S and Pursley, Amber N and Kang, Sung-Hae L and Bi, Weimin and Lalani, Seema R and Bacino, Carlos A and Vast, Mala and Marks, Karen and Patton, Michael and Olofsson, Peter and Patel, Ankita and Veltman, Joris A and Cheung, Sau Wai and Shaw, Chad A and Vissers, Lisenka E L M and Vermeesch, Joris R and Lupski, James R and Stankiewicz, Pawe{\l}} }