Lafora disease is a severe, autosomal recessive, progressive myoclonus epilepsy. The disease usually manifests in previously healthy adolescents, and death commonly occurs within 10 years of symptom onset. Lafora disease is caused by loss-of-function mutations in EPM2A or NHLRC1, which encode laforin and malin, respectively. The absence of either protein results in poorly branched, hyperphosphorylated glycogen, which precipitates, aggregates and accumulates into Lafora bodies. Evidence from Lafora disease genetic mouse models indicates that these intracellular inclusions are a principal driver of neurodegeneration and neurological disease. The integration of current knowledge on the function of laforin-malin as an interacting complex suggests that laforin recruits malin to parts of glycogen molecules where overly long glucose chains are forming, so as to counteract further chain extension. In the absence of either laforin or malin function, long glucose chains in specific glycogen molecules extrude water, form double helices and drive precipitation of those molecules, which over time accumulate into Lafora bodies. In this article, we review the genetic, clinical, pathological and molecular aspects of Lafora disease. We also discuss traditional antiseizure treatments for this condition, as well as exciting therapeutic advances based on the downregulation of brain glycogen synthesis and disease gene replacement.

Every fourth woman suffers from uterine leiomyomas (ULs) -benign uterine wall tumors -at some point in premenopausal life. ULs can cause excessive bleeding, pain and infertility 1 , and are the most common cause of hysterectomy 2 . They emerge through at least three distinct genetic drivers: MED12 or FH mutation, or HMGA2 genomic rearrangement 3 . Here we created large genome-wide data sets by DNA, RNA, ATAC, ChIP and HiChIP sequencing of primary tissues to profoundly understand UL genesis. We discovered somatic mutations in genes encoding six members of the SRCAP histone loading complex 4 , and found that germline mutations in SRCAP complex members YEATS4 and ZNHIT1 predispose to UL. The mutant tumors displayed defective histone variant H2A.Z deposition. In ULs, H2A.Z occupancy correlated positively with chromatin accessibility and gene expression, and negatively with DNA methylation, but these correlations were weak in SRCAP complex mutant tumors. In such tumors, open chromatin emerged at transcription start sites where H2A.Z was lost, associated with upregulation of genes. Furthermore, YEATS4 defects associated with abnormal upregulation of bivalent embryonic stem cell genes, as previously shown in mice 5 . Our work describes a potential novel mechanism of tumorigenesis -epigenetic instability caused by deficient H2A.Z deposition -and suggests that ULs arise through an aberrant differentiation program driven by deranged chromatin, emanating from a small number of mutually exclusive genetic driver mutations.

A truncating mutation in canine ADAMTS17 causes PLL, a well-characterized veterinary disease, which can now be compared to a recently described rare WMS-like disease caused by truncating mutations of the human ADAMTS17 ortholog.

Lafora disease (LD) is an autosomal recessive late onset, progressive myoclonic epilepsy with a high prevalence in the miniature Wirehaired Dachshund. The disease is due to a mutation in the Epm2b gene which results in intracellular accumulation of abnormal glycogen (Lafora bodies). Recent breed-wide testing suggests that the carrier plus affected rate may be as high as 20%. A characteristic feature of the disease is spontaneous and reflex myoclonus; however clinical signs and disease progression are not well described. A survey was submitted to owners of MWHD which were homozygous for Epm2b mutation (breed club testing program) or had late onset reflex myoclonus and clinical diagnosis of LD. There were 27 dogs (11 male; 16 female) for analysis after young mutation-positive dogs that had yet to develop disease were excluded. Average age of onset of clinical signs was 6.94 years (3.5–12). The most common initial presenting sign was reflex and spontaneous myoclonus (77.8%). Other presenting signs included hypnic myoclonus (51.9%) and generalized seizures (40.7%). Less common presenting signs include focal seizures, “jaw smacking”, “fly catching”, “panic attacks”, impaired vision, aggression and urinary incontinence. All these clinical signs may appear, and then increase in frequency and intensity over time. The myoclonus in particular becomes more severe and more refractory to treatment. Signs that developed later in the disease include dementia (51.9%), blindness (48.1%), aggression to people (25.9%) and dogs (33.3%), deafness (29.6%) and fecal (29.6%) and urinary (37.0%) incontinence as a result of loss of house training (disinhibited type behavior). Further prospective study is needed to further characterize the canine disease and to allow more specific therapeutic strategies and to tailor therapy as the disease progresses.

Primary lens luxation (PLL) is a well-recognized, painful and potentially blinding inherited ocular condition in dogs. We screened PLL-affected dogs of 30 different breeds, to identify those which carried a previously described c.1473+1 G>A mutation in ADAMTS17 that is associated with PLL in Miniature Bull terriers, Lancashire Heelers, and Jack Russell terriers. This ADAMTS17 mutation was identified in PLL-affected dogs from 14 additional breeds. PLL-affected dogs from some breeds (most notably the Shar pei and the Brittany spaniel) did not carry the G1473+1A ADAMTS17 mutation, indicating they must suffer from a genetically distinct form of the condition. We also estimated the frequency of this ADAMTS17 mutation in some of the breeds. Our findings indicate the mutation segregates in a large number of different breeds of dog, many of which are terriers or breeds with terrier co-ancestry, but some of which have more diverse origins. Our results also indicate that the mutation is present at high frequency within most of the breeds in which it segregates. In the miniature bull terrier breed estimates of mutation frequency ranged from 0.27 to 0.39, corresponding to 7.3-15.2% PLL-affected dogs in this breed. We also identified an increased risk of PLL associated with heterozygosity at ADAMTS17, suggesting that carriers carry a low risk of developing PLL.

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Lafora disease is a fatal progressive myoclonus epilepsy. At root, it is due to constant acquisition of branches that are too long in a subgroup of glycogen molecules, leading them to precipitate and accumulate into Lafora bodies, which drive a neuroinflammatory response and neurodegeneration. As a potential therapy, we aimed to downregulate glycogen synthase, the enzyme responsible for glycogen branch elongation, in the disease’s mouse models. We synthesized an antisense oligonucleotide (Gys1-ASO) that targets the mRNA of the brain-expressed glycogen synthase 1 gene (Gys1). We administered Gys1-ASO by intracerebroventricular injection and analyzed the pathological hallmarks of Lafora disease, namely glycogen accumulation, Lafora body formation, and neuroinflammation. Gys1-ASO prevented Lafora body formation in young mice that had not yet formed them. In older mice that already exhibited Lafora bodies, Gys1-ASO inhibited further accumulation, markedly preventing large Lafora bodies characteristic of advanced disease. Inhibition of Lafora body formation was associated with prevention of astrogliosis and strong trends towards correction of dysregulated expression of disease immune and neuroinflammatory markers. Lafora disease manifests gradually in previously healthy teenagers. Our work provides proof of principle that an antisense oligonucleotide targeting the GYS1 mRNA could prevent, and halt progression of, this catastrophic epilepsy.

Primary glaucoma is one of the most common causes of irreversible blindness both in humans and in dogs. Glaucoma is an optic neuropathy affecting the retinal ganglion cells and optic nerve, and elevated intraocular pressure is commonly associated with the disease. Glaucoma is broadly classified into primary open angle (POAG), primary closed angle (PCAG) and primary congenital glaucoma (PCG). Human glaucomas are genetically heterogeneous and multiple loci have been identified. Glaucoma affects several dog breeds but only three loci and one gene have been implicated so far. We have investigated the genetics of primary glaucoma in the Norwegian Elkhound (NE). We established a small pedigree around the affected NEs collected from Finland, US and UK and performed a genome-wide association study with 9 cases and 8 controls to map the glaucoma gene to 750 kb region on canine chromosome 20 (praw = 4.93×10−6, pgenome = 0.025). The associated region contains a previously identified glaucoma gene, ADAMTS10, which was subjected to mutation screening in the coding regions. A fully segregating missense mutation (p.A387T) in exon 9 was found in 14 cases and 572 unaffected NEs (pFisher = 3.5×10−27) with a high carrier frequency (25.3%). The mutation interrupts a highly conserved residue in the metalloprotease domain of ADAMTS10, likely affecting its functional capacity. Our study identifies the genetic cause of primary glaucoma in NEs and enables the development of a genetic test for breeding purposes. This study establishes also a new spontaneous canine model for glaucoma research to study the ADAMTS10 biology in optical neuropathy.