{'fraction_non_alphanumeric': 0.028890347997373604, 'fraction_numerical': 0.011818778726198293, 'mean_word_length': 5.655021834061135, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
In vivo exploration of the significance of N‐glycolylneuraminic acid exclusion from the vertebrate brain (787.3)

Sialic acids are acidic sugars often occupying the non‐reducing terminus of glycans. In mammals, the major sialic acids are N‐acetylneuraminic acid (Neu5Ac) and N‐glycolylneuraminic acid (Neu5Gc). The nucleotide donor CMP‐Neu5Gc is biosynthesized from CMP‐Neu5Ac by CMP‐Neu5Ac hydroxylase (Cmah). Regulation of Cmah expression results in markedly varying ratios of Neu5Ac and Neu5Gc among different tissues in different animal species. However, the brain shows extremely low Neu5Gc expression (<3%) in all species tested to date. We used Neu5Gc‐overexpressing Cmah transgenic mice to ask if brain expression of Neu5Gc negatively affects development and/or function. In initial attempts using CMV or NSE promoters, no live mice overexpressing Neu5Gc were obtained, suggesting toxicity. Next, we applied a Cre‐loxP approach for controlled transgene‐derived Cmah expression by Cre recombinase. Interestingly, forced Cmah expression did not show lethality or gross developmental defects with several different Cre mouse lines. The transgenic mice showed remarkably high and widely distributed Neu5Gc expression in the whole brain. Thus, the embryonic lethality seen initially is due to some other effect of Neu5Gc overexpression. This mouse model will provide new insights in understanding unique features of sialic acids in the brain. We are currently studying sialoglycan structures and phenotypes in such mice.