Compositions and methods for genomic editing by insertion of donor polynucleotides

A donor polynucleotide comprising a non-replicative double-stranded DNA molecule (dsDNA) comprising a nucleotide sequence which corrects a mutation that causes Glycogen Storage Disease 1a in a genomic DNA molecule (gDNA) molecule in a cell, wherein the mutation is a protein-coding mutation proximal to a 3′ splice site in the human G6PC gene, the donor polynucleotide comprising,

• (i) a first strand comprising from 5′ to 3′:
• (a) a nucleotide sequence comprising splicing signals to control processing of a precursor mRNA (pre-mRNA) transcribed from the gDNA, wherein the splicing signals are a branch point, a polypyrimidine tract, and a natural or enhanced 3′ splice site;
• and (b) a nucleotide sequence comprising an exonic sequence which corrects the mutation;
• and
• (ii) a second strand comprising a nucleotide sequence complementary to the first strand, wherein the donor polynucleotide is at least 25 and up to 500 nucleotides in length, and wherein when the donor polynucleotide is introduced into the cell in combination with a site-directed nuclease, a non-homologous end-joining (NHEJ) DNA repair pathway inserts the donor polynucleotide into a double-stranded DNA break (DSB) introduced into the gDNA by the site-directed nuclease at a location proximal to the mutation, thereby correcting the mutation.