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Gene & Protein in Disease Enhancing fertility with CRISPR

1. Introduction reproductive biology holds the potential for CRISPR-based
genetic engineering of animal models, gene therapy for
The genome serves as the fundamental code governing heritable diseases, and assisted reproductive techniques.
the transmission of traits in living organisms and is the The review aims to provide an in-depth study of ongoing
medium specifying hereditary patterns. Mammalian research, challenges, limitations, and future prospects in
bodies, including humans, consist of trillions of cells, this field. We explore the applications of CRISPR-based
classified into germ cells known as gametes and autosomal genetic engineering in reproductive biology, discussing
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cells called somatic cells. Germline cells contain a single set potential applications such as creating genetically
of chromosomes, constituting a complete genome, while modified animal models, gene therapy for reproductive
somatic cells typically possess two sets of chromosomes, diseases, manipulation of gametes and embryos, and
representing two genomes. 2
assisted reproduction techniques. The review provides
Scientists and researchers now have the privilege of a comprehensive analysis of the current state of research
accessing the complete sequence of the human genome, in this field, highlighting benefits, challenges, and ethical
opening avenues for promising opportunities in genome considerations associated with the use of CRISPR in
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modification for enhancement and therapeutic benefits. reproductive biology.
This capability, known as gene editing or genetic
engineering, involves making changes to nucleotide 2. CRISPR technology
sequences in DNA, inducing artificial mutations through 2.1. Basics of CRISPR
the insertion, deletion, or replacement of nucleotide bases.
4
Three prominent gene editing techniques – transcription CRISPR, identified in the DNA of archaea and bacteria,
activator-like effector nucleases (TALENS), zinc finger serves as a defense mechanism against foreign DNA, such
nuclease (ZFN), and clustered regularly interspaced short as bacteriophages, effectively neutralizing any undesirable
palindromic repeats–associated systems (CRISPR-Cas) effects of these foreign agents and operating as an immune
– are currently in use, with CRISPR-Cas emerging as the response. 17,18 Japanese researchers first discovered CRISPR
most efficient for genome editing. 5 in 1987 during the study of the bacterial immune system at
Osaka University. The initial evidence of their existence
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Discovered in 1987 in Escherichia coli, clustered stemmed from the identification of a distinctive repetitive
regularly interspaced short palindromic repeats (CRISPR) DNA sequence in the E. coli genome, later designated as
functions as part of the immune systems in prokaryotes CRISPR. Subsequent discoveries revealed comparable
against viral attacks. Today, CRISPR has diverse sequence patterns in various bacteria, including halophilic
6,7
applications, including gene therapy to eliminate genetic archaea, indicating the evolutionarily conserved nature
diseases, cancer treatment, and addressing mitochondrial of these clusters of repetitive sequences for a crucial
diseases. 8-10 It has been successfully used to edit specific purpose. The connection between CRISPR and Cas
genes, such as HBB, in human tripronuclear zygotes. proteins, initially believed to be involved in DNA repair
11
Recently, the United Kingdom approved Casgevy, a in hyperthermophilic archaea, marked a significant step
CRISPR/Cas9 therapy by Vertex and CRISPR Therapeutics, toward understanding the functional aspects of CRISPR-
for sickle-cell disease and β-thalassemia, demonstrating Cas systems. 7
promising results in trials. 12,13
The gene-editing potential of CRISPR was initially
Reproductive biology research contributes significantly reported in 2012 when Jennifer Doudna and Emmanuelle
to human welfare by advancing diagnostic methods and Charpentier outlined how to employ CRISPR to modify
treatment plans for conditions such as endometriosis, genes in human cells. Their pioneering work on CRISPR
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preeclampsia, and infertility. 14 Understanding earned them the Nobel Prize in Chemistry in 2020. 19,21-23
reproductive processes facilitate the development of Since its inception, CRISPR technology has seen
innovative contraceptive options and improvements in improvements in potency, cost-effectiveness, and efficacy,
assisted reproductive technologies (ARTs), benefiting making it a valuable tool for diagnosing, preventing, and
couples facing infertility. 15,16 treating diseases. In addition, novel nucleases like Cpf1
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CRISPR emerges as the pivotal component within gene have been integrated into the CRISPR system, demonstrating
editing technology, characterized by a single sequence enhanced efficiency compared to Cas9 and the ability to
length of 25 – 50 base pairs that are iteratively repeated. target multiple loci in the genome with a single crRNA
It has been effectively employed to treat various genetic transcript. 21,24 Researchers have developed innovative
diseases, including mitochondrial abnormalities, sickle methods for gene editing at multiple loci while utilizing
cell disease, and cancer. Utilizing CRISPR in advanced the same guide RNA (gRNA). 24,25 In today’s technologically

Volume 3 Issue 1 (2024) 2 https://doi.org/10.36922/gpd.2701