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Developmental Biology - In Womb Therapies

Correcting Genes In The Womb

Findings in mice reveal possibilities for fetal drug therapy for Usher syndrome deafness...


New research led by hearing scientists at Oregon Health & Science University suggests an avenue to treat and prevent intractable genetic disorders before birth.

Researchers at the Oregon Hearing Research Center, working with mice, injected a specially designed synthetic molecule into the developing inner ear of fetal mice 12 days after fertilization.

The study found that the technique corrected the expression of a mutated gene that causes Usher syndrome, a disorder characterized by deafness and progressive vision loss affecting an estimated 4 to 17 of every 100,000 people.
The technique does not directly translate to clinical applications in people. However, the new research combined with previous findings suggests it may be possible to deliver the drug therapy through amniotic fluid in the womb to the fetus.

The findings will be published in the journal Nucleic Acids Research.

Scientists designed a synthetic AntiSense Oligonucleotide, or ASO, which targets and then attaches to precise nucleic acid sequences. In this case, the molecule was designed to target pre-messenger RNA, a class of molecules that influences when, where, and how strongly genes are expressed in a cell. When scientists injected the ASO into the developing inner ear of fetal mice carrying the gene mutation, the mice developed with no symptoms of Usher syndrome.
"This shows that direct administration of the ASO to the inner ear restored hearing and balance."

John V. Brigande PhD, Principle Investigator, Oregon Hearing Research Center at Oregon Health & Science University (OHSU) and senior author.

Researchers expect to move from a mouse model to nonhuman primates, which more closely model human hearing loss, before the technique would be ready for human clinical trials. Brigande said he expects it will be useful in potentially treating and preventing several types of congenital forms of hearing and balance disorders.

This work represents the latest in several OHSU initiatives to develop new genetic tools to address genetic conditions.

"In our complementary approach to gene editing in early-stage embryos in a dish, we seek to correct gene expression in the fetal inner ear while inside the uterus - and restore hearing and balance," Brigande explains. "We think both approaches have high merit."
On August 2, 2017, researchers in the Center for Embryonic Cell and Gene Therapy, Oregon Health & Science University published a collaborative effort with multiple USA institutions and the Shenzhen Municipal Government of China to use the CRISPR technique to edit genes within human gametes and zygotes. Published in the journal Nature, OHSU researchers generated worldwide attention when they corrected a gene mutation that causes a deadly heart condition in early human embryos.

Abstract
Disabling hearing loss impacts ~466 million individuals worldwide with 34 million children affected. Gene and pharmacotherapeutic strategies to rescue auditory function in mouse models of human deafness are most effective when administered before hearing onset, after which therapeutic efficacy is significantly diminished or lost. We hypothesize that preemptive correction of a mutation in the fetal inner ear prior to maturation of the sensory epithelium will optimally restore sensory function. We previously demonstrated that transuterine microinjection of a splice-switching antisense oligonucleotide (ASO) into the amniotic cavity immediately surrounding the embryo on embryonic day 1313.5 (E1313.5) corrected pre-mRNA splicing in the juvenile Usher syndrome type 1c (Ush1c) mouse mutant. Here, we show that this strategy only marginally rescues hearing and partially rescues vestibular function. To improve therapeutic outcomes, we microinjected ASO directly into the E12.5 inner ear. A single intra-otic dose of ASO corrects harmonin RNA splicing, restores harmonin protein expression in sensory hair cell bundles, prevents hair cell loss, improves hearing sensitivity, and ameliorates vestibular dysfunction. Improvements in auditory and vestibular function were sustained well into adulthood. Our results demonstrate that an ASO pharmacotherapeutic administered to a developing organ system in utero preemptively corrects pre-mRNA splicing to abrogate the disease phenotype.

Authors
Lingyan Wang, J Beth Kempton, Han Jiang, Francine M. Jodelka, Alev M. Brigande, Rachel A Dumont, Frank Rigo, Jennifer J. Lentz, Michelle L. Hastings and John V. Brigande.


Acknowledgements
Funding
This work was supported by grants from the Foundation Fighting Blindness; the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health, including grant numbers R01-DC012596 and RO1-DC014160; National Eye Institute grant R01-EY030499; the National Institute on General Medical Sciences, including grants U54 GM104940 and P30 GM103340; grant number P30 NS061800 from the National Institute on Neurological Disorders and Stroke of the NIH; and donations from the Usher 2020 Foundation and the Ush One See Foundation. All work with animals was reviewed and approved by the OHSU Institutional Animal Care and Use Committee.

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Apr 8 2020   Fetal Timeline   Maternal Timeline   News 



Hearing loss impacts ~466 million individuals worldwide with 34 million children affected. Strategies to rescue auditory function in mouse models of human deafness are the most effective if administered before hearing begins. Research demonstrates how inner ear development was corrected in Usher syndrome type 1c (Ush1c) mice. CREDIT John V. Brigande PhD, OHSU.


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