To assess apoptosis in our model, we compared caspase-3 activation in Caco-2 cells on inserts to the long-established monoculture plate environment. Our results indicate that live WBC6 trophozoites can induce apoptosis in a time-dependent manner. Since sonicated Giardia WBC6 parasites fail to produce the same response, this may indicate this particular Giardia strain mediates host cell death through a direct parasite-epithelial cell interaction. The difference in apoptosis observed between plate and insert cultures at 5 days in our studies is likely due to parasite density in the different culture conditions. Significantly more parasites are observed in the insert environment even though the plate and insert cultures received the same starting density of parasites. These findings suggest that nucleotide divergence does not influence cleavage precision, but that nucleotide bias in the 59 and 39 ends of the loop potentially influences miRNA maturation. Herein, canonical miRNA loop Diperodon sequences were collected, with variations in the loops potentially based on the phenomenon of multiple isomiRs, with the canonical miRNA sequences not necessarily the most dominant sequence. However, according to length distributions and terminal end nucleotide compositions, it can be concluded that loop sequences tend to be longer in higher animal species, with rapid evolution of the loop sequences further driving miRNA gene evolution. Stable isomiR expression profiles indicate relative cleavage, which may be closely related to the dominant nucleotide distributions. This study further enriches the understanding of miRNA biogenesis as it relates to loop sequences across different animal species and among homologous miRNAs, particularly considering the phenomenon of multiple isomiRs. Proteins destined for the secretory pathway are inserted into the ER cotranslationally and subjected to quality control. ER molecular chaperones and folding enzymes such as BiP, calnexin, and protein disulfide isomerase facilitate the correct folding or degradation of these newly synthesized proteins as well as of misfolded proteins. The accumulation of misfolded proteins in the ER beyond the capacity of quality control causes ER stress and induces the unfolded protein response. Further ER stress can cause cellular dysfunction and cell death, resulting in diverse human disorders such as neurodegenerative diseases. Mammalian ER luminal chaperones have a carboxyl terminal Lys-Asp-Glu-Leu amino acid sequence, which is recognized by the KDEL receptor in post-ER compartments. ER chaperones and the KDEL receptor are sorted into the transport vesicles coated with coat protein I complex and retrieved to the ER. Yeast BiP is essential for survival, while the deletion of the retrieval sequence is dispensable because the UPR is activated and the loss of the chaperone in the ER is compensated for. The complete depletion of BiP also has lethal effects on mammalian early embryonic cells. In order to elucidate the physiological processes that are sensitive to the retrieval of BiP during development and adulthood in multi-cellular organisms, we previously produced knock-in mice expressing a D-Pantothenic acid sodium mutant BiP in which the retrieval sequence was deleted by homologous recombination. The homozygous mutant BiP mice died within several hours after birth due to respiratory failure with impaired biosynthesis of the pulmonary surfactant.