Whole-Exome and Transcriptome Sequencing Expands the Genotype of Majewski Osteodysplastic Primordial Dwarfism Type II

Abstract

Microcephalic Osteodysplastic Primordial Dwarfism type II (MOPDII) represents the most common form of primordial dwarfism. MOPD clinical features include severe prenatal and postnatal growth retardation, postnatal severe microcephaly, hypotonia, and an increased risk for cerebrovascular disease and insulin resistance. Autosomal recessive biallelic loss-of-function genomic variants in the centrosomal pericentrin (PCNT) gene on chromosome 21q22 cause MOPDII. Over the past decade, exome sequencing (ES) and massive RNA sequencing have been effectively employed for both the discovery of novel disease genes and to expand the genotypes of well-known diseases. In this paper we report the results both the RNA sequencing and ES of three patients affected by MOPDII with the aim of exploring whether differentially expressed genes and previously uncharacterized gene variants, in addition to PCNT pathogenic variants, could be associated with the complex phenotype of this disease. We discovered a downregulation of key factors involved in growth, such as IGF1R, IGF2R, and RAF1, in all three investigated patients. Moreover, ES identified a shortlist of genes associated with deleterious, rare variants in MOPDII patients. Our results suggest that Next Generation Sequencing (NGS) technologies can be successfully applied for the molecular characterization of the complex genotypic background of MOPDII.

Keywords: ES; MOPDII; Majewski; RNA-Seq; pathogenic variants.

Figure 1

PCNT protein expression in MOPDII Patient 3. Western blotting analysis of pericentrin in cellular extracts from lymphoblastoid cell lines (LCLs) from PCNT wild-type control (lane 1); MOPD II patient 3 (lane 2); PCNT homozygous for c.1523dup (lane 3).

Figure 2

RT-qPCR of IGF1R, IGF2R, RAF, and CREBBP in the three MOPDII patients. For Patients 1 and 2, the mean expression of the indicated genes in three age-matched male children was used as calibrator. For Patient 3, the mean expression of the indicated genes in three age-matched female children was used as calibrator. Data are shown as the average with a standard error of three independent experiments (* p value < 0.05; ** p value < 0.005; *** p value < 0.0005).