CCDC88A Mutations Cause PEHO-Like Syndrome in Humans and Mouse
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doi:10.1093/brain/aww014 BRAIN 2016: 139; 1036–1044 | 1036 REPORT CCDC88A mutations cause PEHO-like syndrome in humans and mouse Michael S. Nahorski,1,Ã Masato Asai,2,Ã Emma Wakeling,3 Alasdair Parker,4 Naoya Asai,2 Natalie Canham,3 Susan E. Holder,3 Ya-Chun Chen,1 Joshua Dyer,1 Angela F. Brady,3 Masahide Takahashi2 and C. Geoffrey Woods1 ÃThese authors contributed equally to this work. Progressive encephalopathy with oedema, hypsarrhythmia and optic atrophy (PEHO) syndrome is a rare Mendelian phenotype comprising severe retardation, early onset epileptic seizures, optic nerve/cerebellar atrophy, pedal oedema, and early death. Atypical cases are often known as PEHO-like, and there is an overlap with ‘early infantile epileptic encephalopathy’. PEHO is considered to be recessive, but surprisingly since initial description in 1991, no causative recessive gene(s) have been described. Hence, we report a multiplex consanguineous family with the PEHO phenotype where affected individuals had a homozygous frame-shift deletion in CCDC88A (c.2313delT, p.Leu772Ãter). Analysis of cDNA extracted from patient lymphocytes unexpectedly failed to show non-sense mediated decay, and we demonstrate that the mutation produces a truncated protein lacking the crucial C-terminal half of CCDC88A (girdin). To further investigate the possible role of CCDC88A in human neurodevelopment we re- examined the behaviour and neuroanatomy of Ccdc88a knockout pups. These mice had mesial-temporal lobe epilepsy, micro- cephaly and corpus callosum deficiency, and by postnatal Day 21, microcephaly; the mice died at an early age. As the mouse knockout phenotype mimics the human PEHO phenotype this suggests that loss of CCDC88A is a cause of the PEHO phenotype, and that CCDC88A is essential for multiple aspects of normal human neurodevelopment. 1 Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK 2 Department of Pathology, Centre for Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466N, Japan 3 North West Thames Regional Genetics Service, Level 8V, London North West Healthcare NHS Trust, Watford Road, Harrow, HA1 3UJ, UK 4 Department of Paediatric Neuroscience, Addenbrooke’s Hospital, Hills Rd, Cambridge, CB2 0QQ, UK Correspondence to: C. Geoffrey Woods, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, CB2 0XY, UK E-mail: [email protected] Correspondence may also be addressed to: Angela F. Brady, North West Thames Regional Genetics Service, Level 8V, London North West Healthcare NHS Trust, Watford Road, Harrow HA1 3UJ, UK E-mail: [email protected] Masahide Takahashi, Department of Pathology, Centre for Neurological Disease and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Received November 17, 2015. Revised December 09, 2015. Accepted December 23, 2015. Advance Access publication February 25, 2016 ß The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. CCDC88A mutations cause PEHO-like syndrome BRAIN 2016: 139; 1036–1044 | 1037 Nagoya, Aichi 466-8550, Japan E-mail: [email protected] Keywords: PEHO syndrome; girdin; neurodevelopmental disorder; epilepsy; microcephaly Abbreviation: PEHO = progressive encephalopathy with oedema, hypsarrhythmia and optic atrophy authors cared for the family for over a decade; all medical care Introduction was within the National Health Service. Results and notes Progressive encephalopathy with oedema, hypsarrhythmia were examined and recorded. and optic atrophy (PEHO) syndrome is rare, of unknown origin, and causes profound intellectual disability with little Exome sequencing if any developmental progress. It was first described in Genomic DNA from affected Patients 1 and 2 (Fig. 2A) was Finnish children in 1991, from where the most complete extracted and analysed by exome sequencing (SureSelect phenotypic data originates (Salonen et al., 1991). Onset Human All Exon 50Mb Kit, Agilent Technologies). occurs usually within the first few weeks of life with affected Potentially pathogenic mutations were identified by compari- children displaying seizures, hypotonia and lack of visual son with the GRCh37 reference human genome, filtering for fixation (Somer, 1993; D’Arrigo et al., 2005). Those affected changes with allele frequencies of 5 1 in 500 in the 1000 thence exhibit early arrest of motor and mental development, Genomes project, and focused on homozygous changes affect- optic atrophy, with radiological examination demonstrating ing both siblings. Any changes were confirmed and tested for severe cerebellar and brainstem atrophy from birth, with expected segregation, by polymerase chain reaction (PCR) and cerebral atrophy developing at a later stage (D’Arrigo et Sanger sequencing. al., 2005). Usually microcephaly is present at birth, but in- evitably there is a progressive reduction in brain growth Reverse transcription polymerase (secondary microcephaly). Prognosis is poor with most pa- chain reaction analysis tients dying before 10 years of age. Inheritance is predicted to be autosomal recessive (Somer, 1993). Clinically there is To analyse possible nonsense mediated decay of mutant CCDC88A, blood samples were taken from Patient 1 and their phenotypic overlap of PEHO syndrome with the early-in- parents, mRNA extracted and reverse transcribed to cDNA. Full fantile epileptic encephalopathies (Cross and Guerrini, details of reverse transcription PCRs (RT-PCRs) undertaken and 2013). Cases lacking either optic atrophy or cerebellar hypo- primers used are detailed in the Supplementary material. plasia are often termed PEHO-like (Chitty et al., 1996). The genetic cause(s) and the underlying pathophysiology of PEHO syndrome are unknown; and there is no known CCDC88A cloning and expression curative therapy. We report a large consanguineous family CCDC88A cloned into the pCAGGS vector has been described with three affected members in two nuclear families. In previously (Enomoto et al., 2005). The c.2313delT mutation affected individuals we identified a homozygous frameshift was introduced into the wild-type CCDC88A sequence by site- mutation in CCDC88A, the gene that encodes the actin directed mutagenesis using the QuikChange II Site-Directed binding protein girdin (GIRDers of actIN filament, also Mutagenesis kit (Agilent), and a haemagglutinin (HA) tag known as APE GIV and HkPP) (Anai et al., 2005; added to the N-terminus. Expression of wild-type and mutant proteins were analysed by western blot. Enomoto et al., 2005; Le-Niculescu et al., 2005; Simpson et al., 2005). We show that the mutation results in the absence of full length, functional CCDC88A protein. To CCDC88A knockout mouse further investigate the function of CCDC88A in mamma- The CCDC88A knockout mice and conditional Nestin–cre lian brain function we examined CCDC88A-deficient mice knockout mice strains have been reported previously and compare their phenotype and CNS architecture to our (Kitamura et al., 2008; Asai et al., 2012). Full details of patients. Our results reveal novel insights into the under- brain dissection, staining and analysis are described in the lying developmental, neuroanatomical and molecular de- Supplementary material. fects of CCDC88A deficiency in mammals. Materials and methods Results Materials and methods are described in detail in the Clinical features of the family Supplementary material. The clinical features of the affected children are summar- ized in Table 1, and individual histories are given in the Subjects Supplementary material. The UK National Research Ethics Service, Cambridge Central All affected children presented at birth with microcephaly Research Ethics committee gave permission for our study. The [Occipito-frontal head circumference (OFHC) of À 3 1038 | BRAIN 2016: 139; 1036–1044 M. S. Nahorski et al. standard deviation (SD) to À 4 SD, typically 529 cm] and considered that the better phenotypic diagnosis for the moderately severe hypotonia. Weight and length at birth family was PEHO-like syndrome. were normal. Excepting the microcephaly, they were not dysmorphic, nor did they have any extracranial congenital Identification of CCDC88A mutation anomalies. All spent 2–4 weeks in hospital until satisfactory breathing and feeding were established. All developed seiz- To identify the causative gene mutation in this family, ures associated with anoxia presenting at birth or by 1 exome analysis was performed on genomic DNA from month. In all three subjects this progressed to flexion in- two affected children (Patients 1 and 2, Fig. 2A), the raw fantile spasms with hypsarrhythmia on EEG within the first sequences mapped to the GRCh37 reference human year of life. Seizures became tonic/clonic by the third year, genome, and any possible mutations shared in both chil- fits occurred frequently (at least weekly throughout life), dren analysed for their potential to cause PEHO syndrome. status epilepticus necessitating hospital admission at least We prioritized the search for mutations that would poten- once in all three, and their seizures were persistently diffi- tially alter the encoded protein (nonsense/frameshift/splice cult to control necessitating frequent changes