High-resolution temporal and regional mapping of MAPT expression and splicing in human brain development

Abstract

The microtubule associated protein tau plays a critical role in the pathogenesis of neurodegenerative disease. Recent studies suggest that tau also plays a role in disorders of neuronal connectivity, including epilepsy and post-traumatic stress disorder. Animal studies have shown that the MAPT gene, which codes for the tau protein, undergoes complex pre-mRNA alternative splicing to produce multiple isoforms during brain development. Human data, particularly on temporal and regional variation in tau splicing during development are however lacking. In this study, we present the first detailed examination of the temporal and regional sequence of MAPT alternative splicing in the developing human brain. We used a novel computational analysis of large transcriptomic datasets (total n = 502 patients), quantitative polymerase chain reaction (qPCR) and western blotting to examine tau expression and splicing in post-mortem human fetal, pediatric and adult brains. We found that MAPT exons 2 and 10 undergo abrupt shifts in expression during the perinatal period that are unique in the canonical human microtubule-associated protein family, while exon 3 showed small but significant temporal variation. Tau isoform expression may be a marker of neuronal maturation, temporally correlated with the onset of axonal growth. Immature brain regions such as the ganglionic eminence and rhombic lip had very low tau expression, but within more mature regions, there was little variation in tau expression or splicing. We thus demonstrate an abrupt, evolutionarily conserved shift in tau isoform expression during the human perinatal period that may be due to tau expression in maturing neurons. Alternative splicing of the MAPT pre-mRNA may play a vital role in normal brain development across multiple species and provides a basis for future investigations into the developmental and pathological functions of the tau protein.

Engineered Cerebral Organoids Recapitulate Adult Tau Expression and Disease-relevant Changes in Tau Splicing

“…RNA from post-mortem brain was used as a positive control, and bands of 112bp (0N), 199bp (1N) and 286bp (2N) could be seen following separation by electrophoresis. As expected, 1N was the most predominant isoform in brain-derived cDNA followed by 0N and 2N (12,15,21). In contrast, the band corresponding to 0N tau was the most predominant in enCORs of all genotypes at 100 DIV, consistent with a predominant expression of 0N isoforms during early development (12,32).…”

“…As expected, 1N was the most predominant isoform in brain-derived cDNA followed by 0N and 2N (12,15,21). In contrast, the band corresponding to 0N tau was the most predominant in enCORs of all genotypes at 100 DIV, consistent with a predominant expression of 0N isoforms during early development (12,32). A faint band corresponding to 1N tau isoforms could also be observed, and in some enCORs a faint 2N band could be seen, although this was variable.…”

“…Multiple groups have used this approach to successfully study tauopathies (11). While this is a promising approach, a major challenge is overcoming the developmental regulation of tau; during fetal stages, the 0N3R isoform constitutes the majority of tau (12,13), a phenomenon recapitulated in iPSC-neurons by multiple groups (14,15). Although multiple tau isoforms can be observed in iPSC-neurons, this can require long-term culture (150-365 days) and/or the presence of splice mutations in MAPT, and it remains to be determined whether these recapitulate the precise stoichiometry of tau splicing seen in the adult brain (14,(16)(17)(18)(19).…”

Accelerated neuronal and synaptic maturation by BrainPhys medium increases Aβ secretion and alters Aβ peptide ratios from iPSC-derived cortical neurons

“…3R tau binds less tightly to microtubule 52 , which is necessary during development. 4R tau, where exon 10 is included, is absent in the fetal brain but increases dramatically during the prenatal-to adult period 31 . To determine the neuronal maturation state, we investigated presence of tau exon 10 in both conditions.…”

“…(II) The area of GFAP signal per image was quantified and related to the number of DAPI-stained nuclei in the same image. Three-six images/experiment and www.nature.com/scientificreports www.nature.com/scientificreports/ splice form of tau including exon 10 which is present in the cortex of children and adults, but not in the fetal cortex 31 . The exon 10 splice variant could not be detected in either condition at this neuronal differentiation stage (Fig.…”