Diagnostic yield of chromosomal microarray and trio whole exome sequencing in cryptogenic cerebral palsy.

OBJECTIVE: To determine the yield of genetic diagnoses using chromosomal microarray (CMA) and trio whole exome sequencing (WES), separately and combined, among patients with cryptogenic cerebral palsy (CP). METHODS: Trio WES of patients with prior CMA analysis for cryptogenic CP, defined as disabling, non-progressive motor symptoms beginning before the age of 3 years without known cause. RESULTS: Given both CMA analysis and trio WES, clinically significant genetic findings were identified for 58% of patients (26 of 45). Diagnoses were eight large CNVs detected by CMA and 18 point mutations detected by trio WES. None had more than one severe mutation. Approximately half of events (14 of 26) were de novo. Yield was significantly higher in patients with CP with comorbidities (69%, 22 of 32) than in those with pure motor CP (31%, 4 of 13; p=0.02). Among patients with genetic diagnoses, CNVs were more frequent than point mutations among patients with congenital anomalies (OR 7.8, 95% CI 1.2 to 52.4) or major dysmorphic features (OR 10.5, 95% CI 1.4 to 73.7). Clinically significant mutations were identified in 18 different genes: 14 with known involvement in CP-related disorders and 4 responsible for other neurodevelopmental conditions. Three possible new candidate genes for CP were ARGEF10, RTF1 and TAOK3. CONCLUSIONS: Cryptogenic CP is genetically highly heterogeneous. Genomic analysis has a high yield and is warranted in all these patients. Trio WES has higher yield than CMA, except in patients with congenital anomalies or major dysmorphic features, but these methods are complementary. Patients with negative results with one approach should also be tested by the other.

The novel R211Q POP1 homozygous mutation causes different pathogenesis and skeletal changes from those of previously reported POP1-associated anauxetic dysplasia.

Processing of Precursor RNA 1 (POP1) is a core protein component shared by two essential closely related eukaryotic ribonucleoprotein complexes: RNase MRP (the mitochondrial RNA processing ribonuclease) and RNase P. Recently, five patients harboring mutations in POP1 have been reported with severe spondylo-epi-metaphyseal dysplasia and extremely short stature. We report a unique clinical phenotype resulting from the novel homozygous R211Q POP1 mutation in three patients from one family, presenting with severe short stature but only subtle skeletal dysplastic changes that are merely metaphyseal. The RNA moiety of the RNase-MRP complex quantified in RNA extracted from peripheral lymphocytes was dramatically reduced in affected patients indicating instability of the enzymatic complex. However, pre5.8s rRNA, a substrate of RNase-MRP complex, was not accumulated in patients' RNA unlike in the previously reported POP1 mutations; this may explain the uniquely mild phenotype in our cases, and questions the assumption that alteration in ribosomal biogenesis is the pathophysiological basis for skeletal disorders caused by POP1 mutations. Finally, POP1 mutations should be considered in familial cases with severe short stature even when skeletal dysplasia is not strongly evident.

A Unique Presentation of XY Gonadal Dysgenesis in Frasier Syndrome due to WT1 Mutation and a Literature Review.

Frasier syndrome (FS), a rare disease caused by inherited or de novo mutation in Wilm's Tumor suppressor gene 1 (WT1), is characterized by slow progressive nephropathy, XY gonadal dysgenesis (XY-DSD), and increased risk for gonadal tumors. Early childhood (1-6 years) nephropathy progresses with age to refractory nephrotic syndrome, and end-stage renal failure in late adolescence, when delayed puberty and/or primary amenorrhea are clinically evident. We report a unique case of FS presenting initially with primary amenorrhea at 16 years, without previous or concomitant renal damage. Only subsequently she developed an extremely late-onset nephropathy. Genetic analysis revealed the IVS9 + 5 G>A mutation in intron 9 of the WT1 gene. This clinical presentation and review of WT1 literature highlights the importance of considering FS in the differential diagnosis of patients with 46,XY disorders of Sexual development, even without nephropathy. Furthermore, the identification WT1 gene mutation prior to evident renal dysfunction indicates an immediate and close surveillance of renal function enabling an optimal and timely medical response.

The novel founder homozygous V225M mutation in the HSD17B3 gene causes aberrant splicing and XY-DSD.

PURPOSE: Mutations in the gene HSD17B3 encoding the 17-beta hydroxysteroid dehydrogenase 3 enzyme cause testosterone insufficiency leading to XY disorders of sex development. In this study the clinical and molecular characteristics of three patients from consanguineous families are elucidated. METHODS: We identified three patients from two unrelated families with XY DSD and a novel homozygous HSD17B3:c. 673G>A mutation. The effect of the mutation on splicing was determined in RNA extracted from the testis of one patient. RESULTS: Three patients presented at ages 0.1, 8 and 0.7 years with ambiguous genitalia and an XY Karyotype. Endocrine workup showed normal cortisol and mineralocorticoid levels with a low testosterone/androstenedione ratio. Whole-exome sequencing, carried out in the first family, revealed a homozygous novel mutation in the HSD17B3 gene: c. 673G>A, p. V225M. The same mutation was found by Sanger sequencing in the third unrelated patient. Haplotype analysis of a 4 Mb region surrounding the HSD17B3 gene on chromosome 9 revealed that the mutation resides on the same allele in all three patients. The mutation, being the first nucleic acid on exon 10, affects splicing and causes exon 10 skipping in one of our patients' testes. CONCLUSION: The novel homozygous c. 673G>A, p. V225M mutation in the 17HSDB3 gene is likely a founder mutation and causes severe XY-DSD. It changes a conserved amino acid residue, and also alters 17HSDB3 gene transcription by causing skipping of exon 10, thereby contributing to an imbalance in the relevant protein isoforms and consequently, significant decreased 17HDSB3 enzymatic activity.