Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Comparative Proteomic Analysis of Toxoplasma gondii RH Wild-Type and Four SRS29B (SAG1) Knock-Out Clones Reveals Significant Differences between Individual Strains

Version 1 : Received: 19 May 2023 / Approved: 22 May 2023 / Online: 22 May 2023 (09:03:52 CEST)

A peer-reviewed article of this Preprint also exists.

Hänggeli, K.P.A.; Hemphill, A.; Müller, N.; Heller, M.; Uldry, A.-C.; Braga-Lagache, S.; Müller, J.; Boubaker, G. Comparative Proteomic Analysis of Toxoplasma gondii RH Wild-Type and Four SRS29B (SAG1) Knock-Out Clones Reveals Significant Differences between Individual Strains. Int. J. Mol. Sci. 2023, 24, 10454. Hänggeli, K.P.A.; Hemphill, A.; Müller, N.; Heller, M.; Uldry, A.-C.; Braga-Lagache, S.; Müller, J.; Boubaker, G. Comparative Proteomic Analysis of Toxoplasma gondii RH Wild-Type and Four SRS29B (SAG1) Knock-Out Clones Reveals Significant Differences between Individual Strains. Int. J. Mol. Sci. 2023, 24, 10454.

Abstract

In T. gondii, as well as in other model organisms, gene knock-out using CRISPR-Cas9 is a suitable tool to identify the role of specific genes. The general consensus implies that only the gene of interest is affected by the knock-out. Is this really the case? In a previous study, we have generated knock-out (KO) clones of TgRH88_077450 (SRS29B; SAG1) which differed in the numbers of integrated dihydrofolate-reductase-thymidylate-synthase (MDHFR-TS) drug-selectable marker. Clones 18 and 33 had a single insertion of MDHFR-TS within SRS29B. Clone 6 was disrupted by the insertion of a short unrelated DNA-sequence, but the marker was integrated elsewhere. In clone 30, the marker was inserted into SRS29B and several other MDHFR-TS copies were found in the genome. KO and wild-type (WT) tachyzoites had similar shape, dimensions and vitality. This prompted us to investigate the impact of the genetic engineering as such on the overall proteome patterns of the four clones as compared to the respective WT. Comparative shotgun proteomics of the five strains was performed. Overall, 3236 proteins were identified. Principal component analysis of the proteomes revealed five distinct clusters corresponding to the five strains by both iTop3 and iLFQ algorithms. Detailed analysis of the differentially expressed proteins revealed that the target of the KO, srs29B, was lacking in all KO clones. Besides this protein, twenty other proteins were differentially expressed between KO clones and WT or between different KO clones. The protein exhibiting the highest variation between the five strains was srs36D encoded by TgRH_016110. The deregulated expression of SRS36D was further validated by quantitative PCR. Moreover, the transcript levels of three other selected SRS genes, namely SRS36B, SRS46, and SRS57 exhibited significant differences between individual strains. These results indicate that knocking out a given gene may affect the expression of other genes. Therefore, care must be taken when specific phenotypes are regarded as a direct consequence of the KO of a given gene.

Keywords

genetic manipulation; pleiotropic effects; systems biology

Subject

Biology and Life Sciences, Biochemistry and Molecular Biology

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