Curing the Incurables

This article is a broad review on the strategies to cure the rare genetic disorders which are incurable conditions affecting the development and livelihood of the diseased. Before we start with the strategies, let us first know what are the rare genetic disorders?

• Rare Genetic Disorders

  These disorders are caused by the mutation i.e. sudden change in a gene sequence that results in the production of faulty protein or complete absence of the protein. If there is a problem in a protein, it’s respective function is altered that manifests the disease symptoms. They are considered to be rare because of their prevalence or occurrence in 1 in 3,000 – 5,000 live births. Duchenne Muscular Dystrophy, Cystic Fibrosis and Huntington’s Disease are some common examples of rare genetic disorders to include here. Also, there are ultra-rare genetic disorders in which the prevalence goes to 1 in ~10,000 live births.

  The reason for the gene mutation can be sporadic or random during developmental stages. Also, the mutation can be inherited from the parents being carrier of the pathogenic (disease causing) mutation. Based on the type of disorders, they are classified as dominant and recessive disorders. Dominant disorders in which dominant allele of gene is affected where single gene is sufficient to cause a disease. Recessive disorders in which recessive allele of a gene is affected where two copies from each parent are required to cause a disease. Based on the type of chromosomes involved, there are two types again — autosomal and sex-linked. In autosomal, autosomes are involved, the 22 chromosomes keeping aside a sex chromosome. In sex-linked, only the 23rd chromosome that decides the sex of the offspring is carrying a pathogenic mutation. To sum it up about inheritance, there are 5 types — autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive and Y-linked. One more to mention is about the mitochondria having its own DNA and genes, it can cause genetic disorders too known as mitochondrial genetic disorders. As mitochondria is present in a egg cell or oocyte and sperm gives only the nucleus for the formation of zygote, the mitochondria comes from the mother or a female partner involved.

  Now, let us turn our discussion to the strategies to cure these rare genetic disorders as it’s my area of research interests and I’ve been exploring it since last few years.

• Strategies to cure rare genetic disorders

  As the cause of these disorders is the genetic mutation present within the cells, we have to tackle with the problem at the molecular and cellular level. Previously, it was not possible to play with our own genes and DNA so these disorders were considered to be incurable. But the discovery of crispr-cas9 genome editing tool is a ray of hope to correct the genetic cause of such rare genetic disorders at a molecular level. To integrate this with the iPSCs mediated cell regeneration, correction of a whole cell is possible at a cellular level. I’ve already written on those topics, you’ll find it in the blogs section. Here, we’ll discuss in details how they can be integrated and applied as a strategy to cure rare genetic disorders.

  First, identification of the target pathogenic gene is important. This can be done using appropriate genetic analysis tools like next generation sequencing because diagnosis still remains a challenge for such disorders. So, the diagnosis of a specific condition should be the major focus and active area of research. Next step is to correct the genetic mutation identified by using crispr-cas9 genome editing and iPSCs mediated cell regeneration in an integrated way. This has to be done in-vitro by creating a human disease model from the same subject in study. For crispr-cas9 genome editing, designing the appropriate sgRNA (single guide RNA) is important and donor template as well if required. For iPSCs mediated cell regeneration, Yamanaka factors are required to convert the cells from their differentiated stage to the embryonic-like stem cell stage which can further re-differentiate into the desired lineage. So basically, we have to correct genetic makeup first after identifying the pathogenic gene mutation by using CRISPR tools and then convert that cell to iPSCs with the new potency of regeneration it holds. Last step is to assess for the outcome of regeneration in that cell. This can be done by gene expression analysis and protein analysis for checking the presence of desired mRNA and the functional protein. Overall, these is a personalized approached to consider.

  To translate this clinically, we have to move from lab bench to bedside where patient is completely involved with the procedure so far, from diagnosis or confirming a diagnosis to the outcome of this whole procedure. If the gene expression analysis and protein analysis of in-vitro studies is positive, we can move this ahead towards in-vivo clinical studies. First, isolating cells from the patient. Then, treating the cells with crispr-cas9 and iPSCs technology; alongwith their multiplication in the lab. Lastly, injecting them into the patient back followed by periodic assessments for functional recovery. We can integrate this with rehabilitation as well for the speedy functional and clinical outcomes.

Crispr-cas9 and iPSCs just remained a theoretical studies few years back. But at present times, it has been used in certain parts of the world and research papers are published with the ongoing studies having positive and long-term outcomes. Globally, this area of rare genetic disorders is having a tremendous future with the possibilities it holds as research progresses in advancing molecular science.