Scientific and technological approaches to improve SCNT efficiency in farm animals and pets

Abstract

The birth of Dolly through somatic cell nuclear transfer (SCNT) was a major scientific breakthrough of the last century. Yet, while significant progress has been achieved across the technics required to reconstruct and in vitro culture nuclear transfer embryos, SCNT outcomes in terms of offspring production rates are still limited. Here we provide a snapshot of the practical application of SCNT in farm animals and pets. Moreover, we suggest a path to improve SCNT through alternative strategies inspired by the physiological reprogramming in male and female gametes in preparation for the totipotency required after fertilization. Almost all papers on SCNT focused on nuclear reprogramming in the somatic cells after nuclear transfer. We believe that this is misleading, and even if it works sometimes, it does so in an uncontrolled way. Physiologically, the oocyte cytoplasm deploys nuclear reprogramming machinery specifically designed to address the male chromosome, the maternal alleles are prepared for totipotency earlier, during oocyte nuclear maturation. Significant advances have been made in remodeling somatic nuclei in vitro through the expression of protamines, thanks to a plethora of data available on spermatozoa epigenetic modifications. Missing are the data on large-scale nuclear reprogramming of the oocyte chromosomes. The main message our article conveys is that the next generation nuclear reprogramming strategies should be guided by insights from in-depth studies on epigenetic modifications in the gametes in preparation for fertilization.

Reproduction of Sheep through Nuclear Transfer of Somatic Cells: A Bibliometric Approach

“…In the present study, 124 documents on the reproduction of sheep by SCNT were counted in the WOS database, this quantity of documents is similar to reported in a review carried out for the 25th anniversary of cloning by SCNT. This review published a survey of all published documents (1997-2020) of SCNT classified by species, among which mice, cattle, pigs, goats, and sheep are the species for which more than 100 publications are registered [43].…”

State of the art of nuclear transfer technologies for assisting mammalian reproduction

“…Despite this, SCNT is required to preserve valued animal genetics (particularly by the horse breeding industry, Gambini & Maserati, 2017), for conservation of endangered species (briefly described later in this review), for pets genetic preservation (private companies such as ViaGen pets; https://viagenpets.com and Sinogene; https://www.sinogene.org), and to produce genetically modified animals (Galli & Lazzari, 2021). Several modifications to the initial cloning procedure were emerging, as assisted chemical enucleation, new fusion methods, donor cell and recipient oocyte cycle synchronization, new artificial activation methods, use of epigenetic modulating agents, antioxidants, novel culture systems, among others, leading to differences in SCNT protocols among laboratories (Loi et al, 2021).…”

“…sinogene.org), and to produce genetically modified animals (Galli & Lazzari, 2021). Several modifications to the initial cloning procedure were emerging, as assisted chemical enucleation, new fusion methods, donor cell and recipient oocyte cycle synchronization, new artificial activation methods, use of epigenetic modulating agents, antioxidants, novel culture systems, among others, leading to differences in SCNT protocols among laboratories (Loi et al, 2021).…”

Sperm‐derived RNAs improve the efficiency of somatic cell nuclear transfer (SCNT) through promoting R‐loop formation

“…Somatic cell nuclear transfer (SCNT) is a developing technique to generate a brand new organism from somatic nuclei and oocytes (Gurdon, 1962), which facilitates production of valuable farm, rare and endangered animals (Loi et al, 2021). However, the efficiency of SCNT is low, and thus practical application of SCNT is limited (Heyman et al, 2002).…”