2017 Year in Review and Message from the Editors to Our Reviewers

Next-generation sequencing is revolutionizing identification of novel disease genes and patient diagnosis. Ribonuclease H1 (RNASEH1) digests the RNA present in RNA:DNA hybrids and is present in the nucleus and mitochondria. Bugiardini et al. screened genomic DNAs from 74 probands with multiple deletions/depletion in muscle mtDNA and mendelian progressive external ophthalmoplegia (PEO). They identified 3 pedigrees of Indian ancestry with homozygous or compound heterozygous mutations. In addition to PEO, half of the patients had cerebellar ataxia and dysphagia. In the authors’ cohort, RNASEH1 mutations represented the 4th most common cause of adult-onset PEO with multiple mtDNA deletions after POLG, RRM2B, and TWN.