Derivation of Non-Integration Induced Pluripotent Stem Cells from Fibroblast of Severe Deafness Patients with GJB2 Mutation

In all the connexin-associated human diseases, deafness is one of the most important diseases with high frequency. The mu- tations of GJB2 （gap junction protein β2, also called connexin 26, Cx26） gene link with nonsyndromic or syndromic senso- rineural hearing loss and were shown to account for a large proportion of congenital deaf cases in many studied populations （del Castillo and del Castillo, 2011）. For example, the 235de1C mutation in GJB2 shows the frequency of approximately 1% and is the most frequent mutation in East Asian population （Yan et al., 2003）. Many efforts have been put to study the function of Gjb2 gene in both mouse model and human. In mouse, extensive deletion of Gjb2 causes embryo lethal due to the decreased transplacental glucose uptake, which was not found in human （Takata and Hirano, 1997; Gabriel et al., 1998）. In human, GJB2 deficiency is not able to cause embryo lethal （D＇Andrea et al., 2002）. However, the study of GJB2-associated hearing loss is hampered by many difficulties, such as unobtainable human cochlea and acoustic nerve tissues, and therefore the GJB2-associated hearing loss are underlying mechanisms of still remaining unclear.

Treatment of glutaric aciduria type I(GA-I)via intracerebroventricular delivery of GCDH

Glutaric aciduria type I(GA-I)is an autosomal recessive genetic disorder caused by a deficiency in glutaryl-CoA dehydrogenase(GCDH).Patients who do not receive proper treatment may die from acute encephalopathic crisis.Current treatments for GA-I include a low-lysine diet combined with oral supplementation of L-carnitine.A mouse model of Gcdh^(c.422_428del/c.422_428del)(Gcdh^(−/−))was generated in our laboratory using CRISPR/Cas9.Gcdh^(−/−)mice had significantly higher levels of glutaric acid(GA)in the plasma,liver,and brain than those in wild-type C57BL/6 mice.When given a high-protein diet(HPD)for two days,approximately 60%of Gcdh^(−/−)mice did not survive the metabolic stress.To evaluate whether GCDH gene replacement therapy could be used to provide sustained treatment for patients with GA-1,we prepared a recombinant adeno-associated virus(rAAV)carrying a human GCDH expression cassette and injected it into Gcdh^(−/−)neonates for a proof-of-concept(PoC)study.Our study demonstrated that delivering rAAV to the central nervous system(CNS),but not the peripheral system,significantly increased the survival rate under HPD exposure.Our study also demonstrated that rAAVPHP.eB mediated a higher efficiency than that of rAAV9 in increasing the survival rate.Surviving mice showed dose-dependent GCDH protein expression in the CNS and downregulation of GA levels.Our study demonstrated that AAV-based gene replacement therapy was effective for GA-I treatment and provided a feasible solution for this unmet medical need.