@article {3715,
	title = {Efficient and error-free correction of sickle mutation in human erythroid cells using prime editor-2.},
	journal = {Front Genome Ed},
	volume = {4},
	year = {2022},
	month = {2022},
	pages = {1085111},
	abstract = {<p>Sickle cell anaemia (SCA) is one of the common autosomal recessive monogenic disorders, caused by a transverse point mutation (GAG \&gt; GTG) at the sixth codon of the beta-globin gene, which results in haemolytic anaemia due to the fragile RBCs. Recent progress in genome editing has gained attention for the therapeutic cure for SCA. Direct correction of SCA mutation by homology-directed repair relies on a double-strand break (DSB) at the target site and carries the risk of generating beta-thalassaemic mutations if the editing is not error-free. On the other hand, base editors cannot correct the pathogenic SCA mutation resulting from A \&gt; T base transversion. Prime editor (PE), the recently described CRISPR/Cas 9 based gene editing tool that enables precise gene manipulations without DSB and unintended nucleotide changes, is a viable approach for the treatment of SCA. However, the major limitation with the use of prime editing is the lower efficiency especially in human erythroid cell lines and primary cells. To overcome these limitations, we developed a modular lenti-viral based prime editor system and demonstrated its use for the precise modelling of SCA mutation and its subsequent correction in human erythroid cell lines. We achieved highly efficient installation of SCA mutation (up to 72\%) and its subsequent correction in human erythroid cells. For the first time, we demonstrated the functional restoration of adult haemoglobin without any unintended nucleotide changes or indel formations using the PE2 system. We also validated that the off-target effects mediated by the PE2 system is very minimal even with very efficient on-target conversion, making it a safe therapeutic option. Taken together, the modular lenti-viral prime editor system developed in this study not only expands the range of cell lines targetable by prime editor but also improves the efficiency considerably, enabling the use of prime editor for myriad molecular, genetic, and translational studies.</p>
},
	issn = {2673-3439},
	doi = {10.3389/fgeed.2022.1085111},
	author = {George, Anila and Ravi, Nithin Sam and Prasad, Kirti and Panigrahi, Lokesh and Koikkara, Sanya and Rajendiran, Vignesh and Devaraju, Nivedhitha and Paul, Joshua and Pai, Aswin Anand and Nakamura, Yukio and Kurita, Ryo and Balasubramanian, Poonkuzhali and Thangavel, Saravanabhavan and Marepally, Srujan and Velayudhan, Shaji R and Srivastava, Alok and Mohankumar, Kumarasamypet M}
}
@article {2465,
	title = {Identification of novel HPFH-like mutations by CRISPR base editing that elevate the expression of fetal hemoglobin.},
	journal = {Elife},
	volume = {11},
	year = {2022},
	month = {2022 02 11},
	abstract = {<p>Naturally occurring point mutations in the promoter switch hemoglobin synthesis from defective adult beta-globin to fetal gamma-globin in sickle cell patients with hereditary persistence of fetal hemoglobin (HPFH) and ameliorate the clinical severity. Inspired by this natural phenomenon, we tiled the highly homologous proximal promoters using adenine and cytosine base editors that avoid the generation of large deletions and identified novel regulatory regions including a cluster at the -123 region. Base editing at -123 and -124 bp of promoter induced fetal hemoglobin (HbF) to a higher level than disruption of well-known BCL11A binding site in erythroblasts derived from human CD34+ hematopoietic stem and progenitor cells (HSPC). We further demonstrated in vitro that the introduction of -123T \&gt; C and -124T \&gt; C HPFH-like mutations drives gamma-globin expression by creating a de novo binding site for KLF1. Overall, our findings shed light on so far unknown regulatory elements within the promoter and identified additional targets for therapeutic upregulation of fetal hemoglobin.</p>
},
	keywords = {Adenine, Anemia, Sickle Cell, beta-Globins, beta-Thalassemia, Cell Line, Clustered Regularly Interspaced Short Palindromic Repeats, CRISPR-Cas Systems, Cytosine, Fetal Hemoglobin, gamma-Globins, Gene Editing, Hematopoietic Stem Cells, Humans, Point Mutation, Promoter Regions, Genetic},
	issn = {2050-084X},
	doi = {10.7554/eLife.65421},
	author = {Ravi, Nithin Sam and Wienert, Beeke and Wyman, Stacia K and Bell, Henry William and George, Anila and Mahalingam, Gokulnath and Vu, Jonathan T and Prasad, Kirti and Bandlamudi, Bhanu Prasad and Devaraju, Nivedhitha and Rajendiran, Vignesh and Syedbasha, Nazar and Pai, Aswin Anand and Nakamura, Yukio and Kurita, Ryo and Narayanasamy, Muthuraman and Balasubramanian, Poonkuzhali and Thangavel, Saravanabhavan and Marepally, Srujan and Velayudhan, Shaji R and Srivastava, Alok and DeWitt, Mark A and Crossley, Merlin and Corn, Jacob E and Mohankumar, Kumarasamypet M}
}
