Zollo et al. report that mutations in PRUNE1, a phosphoesterase superfamily molecule, underlie primary microcephaly and profound global developmental delay in four unrelated families from Oman, India, Iran and Italy. The study highlights a potential role for prune during microtubule polymerization, suggesting that prune syndrome may be a tubulinopathy.
EPT1 encodes an enzyme involved in the Kennedy pathway of phospholipid biosynthesis, important for cell membrane integrity. Ahmed et al. identify an EPT1 mutation that impairs enzyme activity and causes complex motor neuron degenerative disease. This is the first human disorder shown to arise through Kennedy pathway dysfunction.
Objective: To identify the genetic cause of pontocerebellar hypoplasia type III (PCH3).
Methods:We studied the original reported pedigree of PCH3 and performed genetic analysis including genome-wide single nucleotide polymorphism genotyping, linkage analysis, wholeexome sequencing, and Sanger sequencing. Human fetal brain RNA sequencing data were then analyzed for the identified candidate gene.
Results:The affected individuals presented with severe global developmental delay and seizures starting in the first year of life. Brain MRI of an affected individual showed diffuse atrophy of the cerebrum, cerebellum, and brainstem. Genome-wide single nucleotide polymorphism analysis confirmed the linkage to chromosome 7q we previously reported, and showed no other genomic areas of linkage. Whole-exome sequencing of 2 affected individuals identified a shared homozygous, nonsense variant in the PCLO (piccolo) gene. This variant segregated with the disease phenotype in the pedigree was rare in the population and was predicted to eliminate the PDZ and C2 domains in the C-terminus of the protein. RNA sequencing data of human fetal brain showed that PCLO was moderately expressed in the developing cerebral cortex.Conclusions: Here, we show that a homozygous, nonsense PCLO mutation underlies the autosomal recessive neurodegenerative disorder, PCH3. PCLO is a component of the presynaptic cytoskeletal matrix, and is thought to be involved in regulation of presynaptic proteins and synaptic vesicles. Our findings suggest that PCLO is crucial for the development and survival of a wide range of neuronal types in the human brain. Neurology ® 2015;84:1745-1750 GLOSSARY dbSNP 5 Single Nucleotide Polymorphism Database; ExAC 5 Exome Aggregation Consortium; FPKM 5 fragments per kilobase of exon per million fragments mapped; GATK 5 Genome Analysis Toolkit; indel 5 insertion-deletion; LOD 5 logarithm of odds; NHLBI 5 National Heart, Lung, and Blood Institute; PCH 5 pontocerebellar hypoplasia; PCH3 5 pontocerebellar hypoplasia type III.
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