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RL1-00630-1: Derivation of hESC Lines with Disease Lesions

Recommendation: Recommended for funding
Scientific Score: 77

First Year Funds Requested: $474,804
Total Funds Requested: $1,424,412

Public Abstract (provided by applicant)

The inner workings of the nervous system which regulate normal body movements, thought processes, feelings and senses are highly complex. How the nervous system relays and receives this variety of information is little understood, although significant inroads are being made to deduce underlying causes of many forms of neurological disorders. Many forms of retardation are caused directly by a failure of the cells within the nervous system to survive or work properly. One of the biggest limitations in this research is the inability to study the disease in the laboratory over the course of the disease. This is because neuronal or brain cells cannot be examined experimentally and ethically until postmortem tissues are obtained. Human embryonic stem cells (hESCs) can differentiate in the laboratory into many of the neural tissues within the human brain and spinal cord. Thus, they are a key to exploring human neurogenesis in vitro. In this proposal, we explore yet another vital use of hESCs, which is to study how neurogenesis is effected in vitro with cells carrying mutations that cause different forms of neurological dysfunction. To date, most of the hESC field has been devoted to deriving purified adult tissues for eventual transplantation therapies. Many hurdles remain, including methods to purify tissues, adequate means to avoid tumorigenesis, immunorejection, and transplantation. While using hESCs for regenerative purposes is the great hope of stem cell biology, the creation of disease specific hESCs is a more tangible and immediate means to both understanding disease and developing drugs to treat disease without having the tremendous cost and hurdles that remain for transplantation therapies. Thus, we argue that a vast and immediate effort should be placed upon the development of hESC lines with specific disease mutations that can be tested in vitro. In this grant we will develop more than 15 new hESC lines that carry mutations that cause neurological disease in children. Our goal is to develop, characterize and distribute hESCs as models for Hurlers Syndrome, Fragile X, Tay Sachs, and Canavan Syndrome so that researchers can study these diseases in the laboratory and test drugs to alleviate them.

Statement of Benefit to California (provided by applicant)

Our goal is to develop human embryonic stem cells that carry mutations that cause neurological diseases in children, including Canavans, Hurler, Tay Sachs, Fragile X and Adrenoleukodystrophy. hESCs can differentiate into neural cell types which means that these lines would provide a valuable tool to study the mechanisms underlying these debilitating diseases and would provide a critical method for drug testing to alleviate the disease symptoms. There is no doubt the development of these hESCs as a tool to understand neurological diseases would benefit the citizens of California, both emotionally and financially.

Review

The goal of this proposal is to derive, characterize and distribute more than 15 new human embryonic stem cell (hESC) lines containing mutations in disease loci that affect neurogenesis, with an emphasis on specific mutations that cause mental retardation in children. Four reasons are given for the derivation of these new lines, and these highlight the importance of the proposal 1) hESCs carrying these mutations would allow mechanistic examination of the affected neuronal tissues in a way not previously possible (need); 2) hESCs differentiate into neurons at a high frequency (feasibility); 3) diseases targeted by this proposal are commonly screened in pre-implantation genetic diagnosis (PGD) (coordination with clinicians); 4) the phenotypes of these diseases are highly penetrant, thus the phenotypes studied in different hESC lines carrying the same mutations are expected to be relatively consistent (feasibility). A collaboration with a PGD laboratory is cited, as well as a derivation success of four new lines with a success rate of 1 in 10. The new lines will be fully characterized and the proposal contains a detailed sharing plan to make the lines available to researchers.

It is clearly important to obtain defined hESC lines harboring genetic causes of different diseases, and those that cause mental retardation would be a very valuable resource given the protocols for neural differentiation of hESC. The use of PGD embryos is the logical way forward. Though a few of these lines exist, they are not readily available. Importantly, the principal investigator (PI) has developed a relationship with a large commercial laboratory that is a leader in PGD and thereby has access to a large number of in vitro fertilization (IVF) clinics. This innovative and impressive collaboration represents an unprecedented opportunity to identify a relatively large number of embryos affected by genetic causes of mental retardation and use them to derive hESCs, all within the guidelines of the National Academy of Sciences. Despite the strength of the collaboration, one reviewer pointed out that insufficient evidence was presented to convince him/her that the number of PGD embryos needed for 15 new lines would be available. The diseases targeted are very rare, and no data on the frequency of PGD is provided either in the application or collaboration letter. Furthermore, concern was raised about the fact that the diseases cited in the letter from the PGD collaborator do not match those targeted in this application, suggesting insufficient communication between the investigators. Overall, though, the significance of this proposal was deemed high, and the work will likely result in expanding the availability of hESC lines with genetic mutations causing mental retardation. This goal was considered a high priority and unique opportunity in the field.

To achieve the proposed aims, the most critical steps will be obtaining consent for using affected embryos and then transporting the embryos from the various IVF facilities to the institution’s hESC facility. The investigators provide a plan to establish a strong and collegial relationship with the IVF clinics, which will be of utmost importance to allow this process to occur in such a short time frame (~2-3 days).

The PI and collaborators are highly qualified experts, with outstanding track records in the field, and the PI’s institution is a perfect setting for these studies. The proposed research is likely to generate hESC lines that have the ability to differentiate into all three germ layers. The plan to share these newly derived lines with researchers through a website and publicity through disease advocacy groups is adequate.

The following Working Group members had a conflict of interest with this application and were therefore recused from participating in review of, discussion of, and voting on the application:

• None