Efficient assembly of a synthetic attenuated SARS-CoV-2 genome in Saccharomyces cerevisiae using multi-copy yeast vectors.

Saccharomyces cerevisiae has been demonstrated to be an excellent platform for the multi-fragment assembly of large DNA constructs through its powerful homologous recombination ability. These assemblies have invariably used the stable centromeric single copy vectors. However, many applications of these assembled genomes would benefit from assembly in a higher copy number vector for improved downstream extraction of intact genomes from the yeast. A review of the literature revealed that large multi-fragment assemblies did not appear to have been attempted in multicopy vectors. Therefore, we devised a toolkit that would enable one to seamlessly transition with the same assembling fragments between a single copy and a multicopy vector. We evaluated the assembly of a 28 kb attenuated SARSCoV- 2 genome (lacking the N gene) from 10 fragments in both single copy and multicopy vector systems. Our results reveal that assembly was comparably efficient in the two vector systems. The findings should add to the synthetic biology toolkit of S. cerevisiae and should enable researchers to utilize any of these vector systems depending on their downstream applications.

Cystinosis: Status of research and treatment in India and the world.

Cystinosis is an autosomally inherited rare genetic disorder in which cystine accumulates in the lysosome. The defect arises from a mutation in the lysosomal efflux pump, cystinosin (or CTNS). Despite the disease being known for more than a century, research, diagnosis, and treatment in India have been very minimal. In recent years, however, some research on cystinosis has been carried out on understanding the pathophysiology and in the development of a humanized yeast model for interrogating the CTNS protein. There has also been a greater awareness of the disease that has been facilitated by the formation of the Cystinosis Foundation of India just over a decade ago. Awareness among primary physicians is critical for early diagnosis, which in turn is critical for proper treatment. Eight different mutations have been observed in cystinosis patients in India, and the mutation spectrum seems different to what has been seen in the US and Europe. Despite these positive developments, there are immense hurdles still to be surmounted. This includes ensuring that the diagnosis is done sooner, making cysteamine more easily available, and, also for the future, to make accessible the promise of gene therapy to cystinosis patients.