Protocol for generating splice isoform-specific mouse mutants using CRISPR-Cas9 and a minigene splicing reporter.

Here, we present a protocol to alter the production of alternatively spliced mRNA variants, without affecting the overall gene expression, through CRISPR-Cas9-engineered genomic mutations in mice. We describe steps for designing guide RNA to direct Cas9 endonuclease to consensus splice sites, producing transgenic mice through pronuclear injection, and screening for desired mutations in cultured mammalian cells using a minigene splicing reporter. Splice isoform-specific mouse mutants provide valuable tools for genetic analyses beyond loss-of-function and transgenic alleles.

Differential developmental deficits in retinal function in the absence of either protein tyrosine sulfotransferase-1 or -2.

To investigate the role(s) of protein-tyrosine sulfation in the retina and to determine the differential role(s) of tyrosylprotein sulfotransferases (TPST) 1 and 2 in vision, retinal function and structure were examined in mice lacking TPST-1 or TPST-2. Despite the normal histologic retinal appearance in both Tpst1(-/-) and Tpst2(-/-) mice, retinal function was compromised during early development. However, Tpst1(-/-) retinas became electrophysiologically normal by postnatal day 90 while Tpst2(-/-) mice did not functionally normalize with age.

Lack of protein-tyrosine sulfation disrupts photoreceptor outer segment morphogenesis, retinal function and retinal anatomy.

To investigate the role(s) of protein-tyrosine sulfation in the retina, we examined retinal function and structure in mice lacking tyrosylprotein sulfotransferases (TPST) 1 and 2. Tpst double knockout (DKO; Tpst1(-/-) /Tpst2 (-/-) ) retinas had drastically reduced electroretinographic responses, although their photoreceptors exhibited normal responses in single cell recordings. These retinas appeared normal histologically; however, the rod photoreceptors had ultrastructurally abnormal outer segments, with membrane evulsions into the extracellular space, irregular disc membrane spacing and expanded intradiscal space.