Identifying candidate genes for 2p15p16.1 microdeletion syndrome using clinical, genomic, and functional analysis
Hani Bagheri, … , Cheryl Y. Gregory-Evans, Evica Rajcan-Separovic
Hani Bagheri, … , Cheryl Y. Gregory-Evans, Evica Rajcan-Separovic
Published March 17, 2016
Citation Information: JCI Insight. 2016;1(3):e85461. https://doi.org/10.1172/jci.insight.85461.
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Research Article Genetics

Identifying candidate genes for 2p15p16.1 microdeletion syndrome using clinical, genomic, and functional analysis

Abstract

The 2p15p16.1 microdeletion syndrome has a core phenotype consisting of intellectual disability, microcephaly, hypotonia, delayed growth, common craniofacial features, and digital anomalies. So far, more than 20 cases of 2p15p16.1 microdeletion syndrome have been reported in the literature; however, the size of the deletions and their breakpoints vary, making it difficult to identify the candidate genes. Recent reports pointed to 4 genes (XPO1, USP34, BCL11A, and REL) that were included, alone or in combination, in the smallest deletions causing the syndrome. Here, we describe 8 new patients with the 2p15p16.1 deletion and review all published cases to date. We demonstrate functional deficits for the above 4 candidate genes using patients’ lymphoblast cell lines (LCLs) and knockdown of their orthologs in zebrafish. All genes were dosage sensitive on the basis of reduced protein expression in LCLs. In addition, deletion of XPO1, a nuclear exporter, cosegregated with nuclear accumulation of one of its cargo molecules (rpS5) in patients’ LCLs. Other pathways associated with these genes (e.g., NF-κB and Wnt signaling as well as the DNA damage response) were not impaired in patients’ LCLs. Knockdown of xpo1a, rel, bcl11aa, and bcl11ab resulted in abnormal zebrafish embryonic development including microcephaly, dysmorphic body, hindered growth, and small fins as well as structural brain abnormalities. Our multifaceted analysis strongly implicates XPO1, REL, and BCL11A as candidate genes for 2p15p16.1 microdeletion syndrome.

Authors

Hani Bagheri, Chansonette Badduke, Ying Qiao, Rita Colnaghi, Iga Abramowicz, Diana Alcantara, Christopher Dunham, Jiadi Wen, Robert S. Wildin, Malgorzata J.M. Nowaczyk, Jennifer Eichmeyer, Anna Lehman, Bruno Maranda, Sally Martell, Xianghong Shan, Suzanne M.E. Lewis, Mark O’Driscoll, Cheryl Y. Gregory-Evans, Evica Rajcan-Separovic

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Figure 5

Protein expression analysis of XPO1, USP34, REL, and BCL11A in human brain.

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Protein expression analysis of XPO1, USP34, REL, and BCL11A in human bra...
(A) Bar graph illustrating expression levels of all 4 genes in 4 different brain regions. Data were obtained from The Human Protein Atlas database (http://proteinatlas.org). N, not detected; L, low; M, medium; H, high. (B) Human fetal brain immunohistochemical staining performed against XPO1 and USP34. For XPO1, mild positivity was seen in immature ependyma or neuroepithelium (black arrows); in the cerebral cortex, positivity was seen in Cajal-Retzius cells (black arrowheads); in immature ependymal cells undergoing mitosis (overlying the germinal matrix), positivity was stronger and associated with the mitotic spindle (red arrowheads). For USP34, strong positive staining was visible in the Purkinje cell layer of fetal brain cerebellar cortex (red arrows), while moderate positivity was seen throughout gray matter in the striatum, tegmentum of the pons, and hippocampus (black arrows); USP34 was diffusely expressed in neurons and could be seen in both the nucleus (N) and cytoplasm (black arrows) for large neurons in the tegmentum of the pons. No staining was visible in white matter or germinal layers. Original magnification, ×200 and ×400, as shown below each image.