Microtubule associated proteins (MAPs), defined as proteins that bind microtubules but are not molecular motors or severing enzymes, play a key role in regulating microtubule stability in neurons. Existing studies of the evolutionary relationships between these proteins are limited to genomic data from a small number of species. We therefore used a large collection of publicly available reference-quality eukaryotic proteomes to carry out a phylogenetic analysis of microtubule associated proteins in both vertebrates and invertebrates. Complete or near-complete reference quality proteomes were obtained from Uniprot. Microtubule associated proteins were identified using InterProtScan, aligned using MUSCLE and then phylogenetic trees constructed using the WAG algorithm. We identified 889 proteins with tubulin binding domains, of which 663 were in eukaryotes, including 168 vertebrates and 64 invertebrates. The vertebrate proteins separated into three families, resembling human MAP 2, MAP4 and MAPT, respectively, while invertebrate MAPs clustered separately. We found significant variation in number of microtubule associated proteins and number of microtubule binding domains between taxa, with fish and mollusks having an unexpectedly high number of MAPs and binding domains, respectively. Our findings represent a novel analysis of the evolution of microtubule associated proteins based on publicly available proteomics data sets. We were able to confirm the phylogeny of MAPs identified based on more limited genomic analyses, and in addition, derived several novel insights on the structure and function of MAPs.

IntroductionThe present study had four aims. First, neuronal injury markers, including neurofilament light (NF-L), total tau, glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase (UCH-L1), were compared between individuals with and without adult-onset myotonic dystrophy type 1 (DM1). Second, the impact of age and CTG repeat on brain injury markers was evaluated. Third, change in brain injury markers across the study period was quantified. Fourth, associations between brain injury markers and cerebral white matter (WM) fractional anisotropy (FA) were identified.MethodsYearly assessments, encompassing blood draws and diffusion tensor imaging on a 3T scanner, were conducted on three occasions. Neuronal injury markers were quantified using single molecule array (Simoa).ResultsThe sample included 53 patients and 70 controls. NF-L was higher in DM1 patients than controls, with individuals in the premanifest phases of DM1 (PreDM1) exhibiting intermediate levels (χ(2)2=38.142, P < 0.001). Total tau was lower in DM1 patients than controls (Estimate = −0.62, 95% confidence interval [CI] −0.95: −0.28, P < 0.001), while GFAP was elevated in PreDM1 only (Estimate = 30.37, 95% CI 10.56:50.19, P = 0.003). Plasma concentrations of UCH-L1 did not differ between groups. The age by CTG interaction predicted NF-L: patients with higher estimated progenitor allelege length (ePAL) had higher NF-L at a younger age, relative to patients with lower CTG repeat; however, the latter exhibited faster age-related change (Estimate = −0.0021, 95% CI −0.0042: −0.0001, P = 0.045). None of the markers changed substantially over the study period. Finally, cerebral WM FA was significantly associated with NF-L (Estimate = −42.86, 95% CI −82.70: −3.02, P = 0.035).InterpretationWhile NF-L appears sensitive to disease onset and severity, its utility as a marker of progression remains to be determined. The tau assay may have low sensitivity to tau pathology associated with DM1.

Transcriptomic investigations of traumatic brain injury (TBI) can give us deep insights into the pathological and compensatory processes post-injury. Thus far, transcriptomic studies in TBI have mostly used microarrays and have focused on rodent models. However, a large animal model of TBI bears a much stronger resemblance to human TBI with regard to the anatomical details, mechanics of injury, genetics, and, possibly, molecular response. Because of the advantages of a large animal TBI model, we investigated the gene expression changes between injured and uninjured sides of pig cerebral cortex after TBI. Given acute inflammation that follows after TBI and the important role that immune response plays in neuroplasticity and recovery, we hypothesized that transcriptional changes involving immune function will be upregulated. Eight female 4-week-old piglets were injured on the right hemisphere with controlled cortical impact (CCI). At 24 h after TBI, pericontusional cortex tissues from the injured side and contralateral cortical tissues were collected. After RNA extraction, library preparation and sequencing as well as gene expression changes between the ipsi- and contralateral sides were compared. There were 6642 genes that were differentially expressed between the ipsi- and contralateral sides, and 1993 genes among them had at least 3-fold differences. Differentially expressed genes were enriched for biological processes related to immune system activation, regulation of immune response, and leukocyte activation. Many of the differentially expressed genes, such as CD4, CD86, IL1A, IL23R, and IL1R1, were major regulators of immune function. This study demonstrated some of the major transcriptional changes between the pericontusional and contralateral tissue at an acute time point after TBI in pigs.

Despite exhibiting tau phosphorylation similar to Alzheimer disease, the human fetal brain is remarkably resilient to tau aggregation and toxicity. To identify potential mechanisms for this resilience, we used co-immunoprecipitation with mass spectrometry to characterize the tau interactome in human fetal, adult, and Alzheimer disease brains. We found significant differences between the tau interactome in fetal and AD brain tissue, with little difference between adult and AD, although these findings are limited by the low throughput and small sample size of these experiments. Differentially interacting proteins were enriched for 14-3-3 domains, and we found that the 14-3-3-β, η, and γ isoforms interacted with phosphorylated tau in Alzheimer disease but not the fetal brain. Since long isoform (4R) tau is only seen in the adult brain and this is one of the major differences between fetal and AD tau, we tested the ability of our strongest hit (14-3-3-β) to interact with 3R and 4R tau using co-immunoprecipitation, mass photometry, and nuclear magnetic resonance (NMR). We found that 14-3-3-β interacts preferentially with phosphorylated 4R tau, forming a complex consisting of two 14-3-3-β molecules to one tau. By NMR, we mapped 14-3-3 binding regions on tau that span the second microtubule binding repeat, which is unique to 4R tau. Our findings suggest that there are isoform-driven differences between the phospho-tau interactome in fetal and Alzheimer disease brain, including differences in interaction with the critical 14-3-3 family of protein chaperones, which may explain, in part, the resilience of fetal brain to tau toxicity.Significance StatementAggregation of phosphorylated tau is the final common pathway for neuronal death across multiple neurodegenerative diseases, but the mechanisms that trigger this process remain unclear. The fetal brain shows high levels of potentially toxic phosphorylated tau without apparent adverse effects, and therefore represents an unprecedented, and heretofore unexplored, opportunity to identify age-related mechanisms for tau toxicity. Our results use a novel data set mapping the tau interactome in human fetal, adult, and AD brain to identify splicing-dependent changes in tau interaction with 14-3-3 family chaperone proteins, which represent highly plausible protective mechanisms in the fetal brain.

1p36 deletion syndrome is the most common terminal deletion syndrome, manifesting clinically as abnormal facies and developmental delay with frequent cardiac, skeletal, urogenital, and renal abnormalities. Limited autopsy case reports describe the neuropathology of 1p36 deletion syndrome. The most extensive single case report described a spectrum of abnormalities, mostly related to abnormal neuronal migration. We report the largest published series of 1p36 autopsy cases, with an emphasis on neuropathologic findings. Our series consists of 3 patients: 2 infants (5-hours old and 23-days old) and 1 older child (11 years). Our patients showed abnormal cortical gyration together with a spectrum of neuronal migration abnormalities, including heterotopias and hippocampal abnormalities, as well as cerebellar hypoplasia. Our findings thus support the role of neuronal migration defects in the pathogenesis of cognitive defects in 1p36 deletion syndrome and broaden the reported neuropathologic spectrum of this common syndrome.