Maternal transcription of non-protein coding RNAs from the PWS-critical region rescues growth retardation in mice

Abstract

Prader-Willi syndrome (PWS) is a neurogenetic disorder caused by loss of paternally expressed genes on chromosome 15q11-q13. The PWS-critical region (PWScr) contains an array of non-protein coding IPW-A exons hosting intronic SNORD116 snoRNA genes. Deletion of PWScr is associated with PWS in humans and growth retardation in mice exhibiting ~15% postnatal lethality in C57BL/6 background. Here we analysed a knock-in mouse containing a 5′HPRT-LoxP-NeoR cassette (5′LoxP) inserted upstream of the PWScr. When the insertion was inherited maternally in a paternal PWScr-deletion mouse model (PWScrp−/m5′LoxP), we observed compensation of growth retardation and postnatal lethality. Genomic methylation pattern and expression of protein-coding genes remained unaltered at the PWS-locus of PWScrp−/m5′LoxP mice. Interestingly, ubiquitous Snord116 and IPW-A exon transcription from the originally silent maternal chromosome was detected. In situ hybridization indicated that PWScrp−/m5′LoxP mice expressed Snord116 in brain areas similar to wild type animals. Our results suggest that the lack of PWScr RNA expression in certain brain areas could be a primary cause of the growth retardation phenotype in mice. We propose that activation of disease-associated genes on imprinted regions could lead to general therapeutic strategies in associated diseases.

Pervasive head-to-tail insertions of DNA templates mask desired CRISPR/Cas9-mediated genome editing events

“…From the assembly of the CRISPR/Cas9 complex and the discovery of direct targeting of specific genomic sequences in vitro 9, 27 , it took only six months to experimentally verify in vitro findings in bacterial and mammalian cells 3,4,28 . The establishment of genetically modified mouse models to study the potential functional roles of genes and their products in human diseases is an important aspect of biomedical studies [29][30][31][32][33] .…”

Prader-Willi locus Snord116 RNA processing requires an active endogenous allele and neuron-specific splicing by Rbfox3/NeuN

“…Currently, two mouse models (PWScr m+/pand Snord116 +/-) carry deletions of the minimal Snord116 PWS critical region, and display postnatal growth deficiency characteristic of the early failure to thrive phenotype exhibited by PWS patients as well as some hyperphagic behavior (18,19). Activation of maternal Snord116 expression rescued the growth retardation and postnatal lethality phenotypes of the PWScr m+/psmall deletion model, supporting Snord116 as the critical PWS region (20). Although the processed snoRNAs have previously been the main focus of studies of the Snord116 locus, transgenic expression of a single copy of Snord116 snoRNA failed to rescue the phenotype of a Snrpn-Ube3a deletion mouse model, suggesting either that the Snord116 functional unit is not restricted solely to the snoRNAs or that multiple copies are required (19,21).…”

“…Although the processed snoRNAs have previously been the main focus of studies of the Snord116 locus, transgenic expression of a single copy of Snord116 snoRNA failed to rescue the phenotype of a Snrpn-Ube3a deletion mouse model, suggesting either that the Snord116 functional unit is not restricted solely to the snoRNAs or that multiple copies are required (19,21). Re-introduction of multiple copies of Snord116 snoRNAs expressed from the introns of another host gene failed to rescue the growth retardation phenotype of PWScr m+/pmice, highlighting the functional significance of the 116HG (20). Importantly, the regulation of circadian and metabolic gene expression by 116HG leads to dysregulated energy expenditure in mice deficient for paternal Snord116, suggesting that the lncRNA 116HG may play role in the pathogenesis of PWS (14).…”

Genotype-Phenotype Relationships and Endocrine Findings in Prader-Willi Syndrome

“…A minimal critical region has emerged implicating that the SNORD116 cluster is crucial for most of the PWS phenotype, based on clinical evidence on rare patients with small deletions or translocations (11,(125)(126)(127)(128). Experimental studies on Snord116-KO mice displayed PWS features such as post-natal growth retardation and hyperphagia (129)(130)(131)(132). Remarkably, a Snord116-KO mice model specifically in NPY neurons in the hypothalamic arcuate nucleus summarized the same overall phenotype observed in mice lacking Snord116 globally; low birth weight, increased body weight gain in early adulthood, increased energy expenditure and hyperphagia (130).…”