Repeat Instability, DNA Mismatch Repair and Potential for Drug Development in Repeat Expansion Disorders

Dear Colleagues,

The expansion of certain simple sequence repeats is known to be associated with a growing number of inherited human disorders, primarily neurological ones, including fragile X syndrome, myotonic dystrophy types 1 and 2, Huntington disease, multiple spinocerebellar ataxias, dentatorubral-pallidoluysian atrophy, spinal and bulbar muscular atrophy, Friedreich ataxia, amyotrophic lateral sclerosis and Fuchs corneal dystrophy. The disease-associated repeats are genetically unstable. Germline repeat instability frequently leads to an increase in repeat length from one generation to the next, and somatic repeat instability leads to an increase in repeat length in specific cell types throughout the lifetime of the individual. In general, the more repeats an individual inherits, the more severe the symptoms and the earlier the age at onset. Besides the length of the inherited disease-causing repeat, the rate at which somatic repeat expansions accumulate in particular cell types is a likely determinant of disease progression and severity. Several DNA mismatch repair proteins have been linked to disease severity and somatic expansion of the disease-causing repeat in multiple repeat expansion disorders. This suggests the existence of a pathogenic DNA mismatch mechanism, common to multiple repeat expansion disorders, operating through its direct effect on the somatic expansion of the disease-causing repeat. This shared somatic repeat expansion mechanism offers a therapeutic opportunity for strategies aiming at slowing down the accumulation of somatic expansions, as some could be applicable to multiple disorders.

This Special Issue aims to highlight recent advances in the field, emphasising commonalities in repeat instability across various expansion disorders. By fostering a deeper understanding of the shared mechanisms, the issue aims to inspire innovative solutions for effective therapeutic interventions for repeat expansion disorders.

This Special Issue invites original studies and review articles covering, but not restricted to, the following themes:

• Accurate genotyping of repeat expansions;
• Precise measurement of repeat instability;
• Identification and validation of new targets;
• Effective drug delivery methods;
• Establishment of target engagement biomarkers.

Dr. Marc Ciosi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• repeat instability
• inherited human disorders
• drug delivery
• DNA mismatch repair
• biomarkers
• unstable repeat expansions