Biology subjects

Kariuki, S. N.

Publications and source records attributed to Kariuki, S. N..

3 recordsLinked to original sources

bioRxiv2022

The erythrocyte membrane properties of beta thalassaemia heterozygotes and their consequences for Plasmodium falciparum invasion

Malaria parasites such as Plasmodium falciparum have exerted formidable selective pressures on the human genome. Of the human genetic variants associated with malaria protection, beta thalassaemia (a haemoglobinopathy) was the earliest to be associated with malaria prevalence. However, the malaria protective properties of beta thalassaemic erythrocytes remain unclear. Here we studied the mechanics and surface protein expression of beta thalassaemia heterozygous erythrocytes, measured their susceptibility to P. falciparum invasion, and calculated the energy required for merozoites to invade them. We found invasion-relevant differences in beta thalassaemic cells versus matched controls, specifically: elevated membrane tension, reduced bending modulus, and higher levels of expression of the major invasion receptor basigin. However, these differences acted in opposition to each other with respect to their likely impact on invasion, and overall we did not observe beta thalassaemic cells to have lower P. falciparum invasion efficiency for any of the strains tested.

microbiology↗

bioRxiv2019

Production of Hybrid Rice seeds using environment sensitive genic male sterile (EGMS) and basmati rice lines in Kenya

Photoperiod-sensitive genic male sterile rice (PGMS) lines IR-73827-23-76-15-7 S, IR-75589-31-27-8-33S referred to as P1 and P2, and IR-77271-42-25-4-36S, thermo-sensitive genic male sterile (TGMS) line referred to as T were obtained from International Rice research Institute. These lines, collectively known as environment genic male sterile lines, were sown under greenhouse growth conditions where temperatures were more than 34{degrees}C with an objective of inducing complete male gamete sterility in them. Results indicated that high temperature growth conditions induces complete male gamete sterility in both the PGMS and TGMS lines. The impact of this is that, it will be possible to produce pure basmati hybrid rice seed in the tropical regions without contamination with pure breed lines. The male sterile PGMS/TGMS were pollinated with pollen from basmati370 and 217 grown under natural conditions and some hybrid seeds were obtained. This shows that high temperature emasculated the male gametes but not female ones. The conclusion is that it is possible to induce complete male gamete sterility in PGMS and TGMS under greenhouse in tropical growth conditions, and to produce hybrid rice seeds. This makes basmati hybrid rice seed production in Kenya a viable venture.

plant biology↗

bioRxiv2018

Red blood cell tension controls Plasmodium falciparum invasion and protects against severe malaria in the Dantu blood group

Malaria has had a major effect on the human genome, with many protective polymorphisms such as sickle cell trait having been selected to high frequencies in malaria endemic regions1, 2. Recently, we showed that a novel blood group variant, Dantu, provides 74% protection against all forms of severe malaria in homozygous individuals3-5. This is a similar degree of protection to sickle cell trait and considerably greater than the most advanced malaria vaccine, but until now the mechanism of protection has been unknown. In the current study, we demonstrate a significant impact of Dantu on the ability of Plasmodium falciparum merozoites to invade RBCs. The Dantu variant was associated with extensive changes to the RBC surface protein repertoire, but unexpectedly the malaria protective effect did not correlate with specific RBC-parasite receptor-ligand interactions. By following invasion using video microscopy, we found a strong link between RBC tension and parasite invasion and, even in non-Dantu RBCs, identified a tension threshold above which RBC invasion did not occur. Dantu RBCs had higher average tension, meaning that a higher proportion of Dantu RBCs could not be invaded. These findings not only provide an explanation for the protective effect of Dantu against severe malaria, but also provide fresh insights into the essential process of P. falciparum parasite invasion, and how invasion efficiency varies across the heterogenous populations of RBCs that are present both within and between individuals.

genetics↗