Temporal and spatial expression of zebrafish mctp genes and evaluation of frameshift alleles of mctp2b

MCTPs (multiple C2 domain proteins with two transmembrane regions) have been proposed as novel endoplasmic reticulum calcium sensors; however, their function remains largely unknown. Here we report the structure of the four mctp genes from zebrafish (mctp1a, mctp1b, mctp2a and mctp2b), their diversity, expression pattern during embryonic development and in adult tissue and the effect of knocking down the expression of Mctp2b by CRISPR/Cas9. The four mctp genes are expressed from early development and exhibit differential expression patterns but are found mainly in the nervous and muscular systems. Mctp2b tagged with fluorescent proteins and expressed in HEK-293 cells and neurons of the fish spinal cord localized mostly in the endoplasmic reticulum but also in lysosomes and late and recycling endosomes. Knocking down mctp2b expression impaired embryonic development, suggesting that the functional participation of this gene is relevant, at least during the early stages of development.

TMEM16A alternative splicing isoforms in Xenopus tropicalis: distribution and functional properties

Oocytes of Xenopus tropicalis elicit a Ca(2+)-dependent outwardly rectifying, low-activating current (ICl,Ca) that is inhibited by Cl(-) channel blockers. When inactivated, ICl,Ca shows an exponentially decaying tail current that is related to currents generated by TMEM16A ion channels. Accordingly, RT-PCR revealed the expression of five alternatively spliced isoforms of TMEM16A in oocytes, which, after expression in HEK-293 cells, gave rise to fully functional Cl(-) channels. Upon hyperpolarization to -80 mV a transient current was observed only in isoforms that carry the exon 1d, coding for two potentially phosphorylatable Threonine residues. The identified isoforms are differentially expressed in several tissues of the frog. Thus, it appears that X. tropicalis oocytes express TMEM16A that gives rise to a Ca(2+)-dependent Cl(-) current, which is different from the previously reported voltage-dependent outwardly rectifying Cl(-) current.

[Microbial interactions with heavy metals]

Living organisms are exposed in nature to heavy metals, commonly present in their ionized species. These ions exert diverse toxic effects on microorganisms. Metal exposure both selects and maintains microbial variants able to tolerate their harmful effects. Varied and efficient metal resistance mechanisms have been identified in diverse species of bacteria, fungi and protists. The study of the interactions between microorganisms and metals may be helpful to understand the relations of toxic metals with higher organisms such as mammals and plants. Some microbial systems of metal tolerance have the potential to be used in biotechnological processes, such as the bioremediation of environmental metal pollution or the recovery of valuable metals. In this work we analyze several examples of the interactions of different types of microbes with heavy metals; these cases are related either with basic research or with possible practical applications.