US Patent 12089574 Humanized skeletal muscle

Described herein is a method for producing a chimeric non-human animal expressing a human a MYF5, MYOD, MRF4 gene or a combination thereof gene comprising: a) generating an MYF5, MYOD, MRF4 or combination thereof null non-human animal cell, wherein both copies of the non-human MYF5, MYOD, MRF4 gene or combination thereof carry a mutation that prevents production of functional MYF5, MYOD, MRF4 protein or combination thereof in said non-human animal; b) creating a MYF5, MYOD, MRF4 or combination thereof null non-human blastocyst by somatic cell nuclear transfer comprising fusing a nucleus from said MYF5, MYOD, MRF4 or combination thereof null non-human animal cell of a) into an enucleated non-human oocyte and activating said oocyte to divide so as to form an MYF5, MYOD, MRF4 or combination thereof null non-human blastocyst; c) introducing human stem cells into the MYF5, MYOD, MRF4 or combination null non-human blastocyst of b); and d) implanting said blastocyst from c) into a pseudopregnant surrogate non-human animal to generate a chimeric non-human animal expressing human MYF5, MYOD, MRF4 or combination thereof.