Northern blot and in situ hybridization analyses for the development of myristoylated alanine-rich c-kinase substrate mRNA in the monkey cerebral cortex

Spatiotemporal Monitoring of Subcellular mRNAs In Situ via Polyadenine-Mediated Dual-Color Sticky Flares

Spatiotemporal monitoring of multiple low-abundance messenger RNAs (mRNAs) is vitally important for the diagnosis and pathologic analysis of cancer. However, it remains a clinical challenge to monitor and track multiple mRNAs location simultaneously in situ at subcellular level with high efficiency. Herein, we proposed polyA-mediated dual-color sticky flares for simultaneous imaging of two kinds of intracellular mRNA biomarkers. Two kinds of fluorescent DNA specific for GalNac-T mRNA and c-Myc mRNA were functionalized onto gold nanoparticles (AuNPs) through efficient polyadenine (polyA) attachment. By tuning polyA length, the lateral spacing and densities of DNA on AuNPs could be precisely engineered. Compared to the traditional thio-DNA-modified nanoprobes, the uniformity, detection sensitivity, and response kinetics of sticky flares were greatly improved, which enables live-cell imaging of mRNAs with enhanced efficiency. With a sticky-end design, the fluorescent DNA could dynamically trace mRNAs after binding with target mRNAs, which realized spatiotemporal monitoring of subcellular mRNAs in situ. Compared to one target mRNA imaging mode, the multiple target imaging mode allows more accurate diagnosis of cancer. Furthermore, the proposed polyA-mediated dual-color sticky flares exhibit excellent cell entry efficiency and low cytotoxicity with a low-cost and simple assembling process, which provide a pivotal tool for multiple targets imaging in living cells.

Molecular composition of the human primary visual cortex profiled by multimodal mass spectrometry imaging

The primary visual cortex (area V1) is an extensively studied part of the cerebral cortex with well-characterized connectivity, cellular and molecular architecture and functions (for recent reviews see Amunts and Zilles, Neuron 88:1086-1107, 2015; Casagrande and Xu, Parallel visual pathways: a comparative perspective. The visual neurosciences, MIT Press, Cambridge, pp 494-506, 2004). In humans, V1 is defined by heavily myelinated fibers arriving from the radiatio optica that form the Gennari stripe in cortical layer IV, which is further subdivided into laminae IVa, IVb, IVcα and IVcβ. Due to this unique laminar pattern, V1 represents an excellent region to test whether multimodal mass spectrometric imaging could reveal novel biomolecular markers for a functionally relevant parcellation of the human cerebral cortex. Here we analyzed histological sections of three post-mortem brains with matrix-assisted laser desorption/ionization mass spectrometry imaging and laser ablation inductively coupled plasma mass spectrometry imaging to investigate the distribution of lipids, proteins and metals in human V1. We identified 71 peptides of 13 different proteins by in situ tandem mass spectrometry, of which 5 proteins show a differential laminar distribution pattern revealing the border between V1 and V2. High-accuracy mass measurements identified 123 lipid species, including glycerolipids, glycerophospholipids and sphingolipids, of which at least 20 showed differential distribution within V1 and V2. Specific lipids labeled not only myelinated layer IVb, but also IVa and especially IVc in a layer-specific manner, but also and clearly separated V1 from V2. Elemental imaging further showed a specific accumulation of copper in layer IV. In conclusion, multimodal mass spectrometry imaging identified novel biomolecular and elemental markers with specific laminar and inter-areal differences. We conclude that mass spectrometry imaging provides a promising new approach toward multimodal, molecule-based cortical parcellation.

Increased expression of the growth-associated protein-43 gene after primary motor cortex lesion in macaque monkeys

We recently showed that changes of brain activity in the ipsilesional ventral premotor cortex (PMv) and perilesional primary motor cortex (M1) of macaque monkeys were responsible for recovery of manual dexterity after lesioning M1. To investigate whether axonal remodeling is associated with M1 lesion-induced changes in brain activity, we assessed gene expression of growth-associated protein-43 (GAP-43) in motor and premotor cortices. Increased expression was observed in the PMv during the period just after recovery and in the perilesional M1 during the plateau phase of recovery. Time-dependent and brain region-specific remodeling may play a role in functional recovery after lesioning M1.

Two myristoylated alanine-rich C-kinase substrate (MARCKS) paralogs are required for normal development in zebrafish

Myristoylated alanine-rich C-kinase substrate (MARCKS) is an actin binding protein substrate of protein kinase C (PKC) and critical for mouse and Xenopus development. Herein two MARCKS paralogs, marcksa and marcksb, are identified in zebrafish and the role of these genes in zebrafish development is evaluated. Morpholino-based targeting of either MARCKS protein resulted in increased mortality and a range of gross phenotypic abnormalities. Phenotypic abnormalities were classified as mild, moderate or severe, which is characterized by a slight curve of a full-length tail, a severe curve or twist of a full-length tail and a truncated tail, respectively. All three phenotypes displayed abnormal neural architecture. Histopathology of Marcks targeted embryos revealed abnormalities in retinal layering, gill formation and skeletal muscle morphology. These results demonstrate that Marcksa and Marcksb are required for normal zebrafish development and suggest that zebrafish are a suitable model to further study MARCKS function.

Expression of protein kinase-C substrate mRNA in the motor cortex of adult and infant macaque monkeys

To understand the molecular and cellular bases of plasticity in the primate motor cortex, we investigated the expression of three protein kinase-C (PKC) substrates: GAP-43, myristoylated alanine-rich C-kinase substrate (MARCKS), and neurogranin, which are key molecules regulating synaptic plasticity. Prominent signals for the three mRNAs were primarily observed in pyramidal cells. Large pyramidal cells in layer V, from which the descending motor tract originates, contained weaker hybridization signals for GAP-43 and neurogranin mRNAs than did the smaller pyramidal cells. We also performed double-label in situ hybridization showing that GAP-43 and neurogranin mRNAs were expressed in a subset of MARCKS-positive neurons. Quantitative analysis showed that the expression was different between the layers: layer VI contained the strongest and layer II the weakest signals for all three mRNAs. The expression levels of GAP-43 and MARCKS mRNA in layer V were higher than in layer III, while the expression level of neurogranin mRNA in layer V was almost the same as in layer III. Developmental analysis from the newborn to adult indicated that the expression levels of the three mRNAs were higher in the infant motor cortex than in the adult. The expression of both GAP-43 and neurogranin mRNAs transiently increased over several months postnatally. The present study showed that the expression of the three PKC substrates was specific to cell types, cortical layers, and postnatal developmental stage. The specific expression may reflect functional specialization for plasticity in the motor cortex of both infants and adults.

Northern blot and in situ hybridization analyses for the neurogranin mRNA in the developing monkey cerebral cortex

Neurogranin is a postsynaptic substrate for protein kinase C, and its expression is related to dendritic spine development and postsynaptic plasticity. Using both Northern blot analysis and in situ hybridization techniques, we investigated the developmental changes of neurogranin expression in the monkey cerebral cortex. In each of four neocortical areas examined, i.e., the prefrontal area (area FD of von Bonin and Bailey), the temporal association area (TE), the primary somatosensory area (PB), and the primary visual area (OC), the Northern blot analysis showed that the amount of neurogranin mRNA was low during the prenatal and perinatal periods until postnatal day 8. It increased during postnatal development and reached its peak value at postnatal day 70 (in area OC) or postnatal month 6 (in area FD, TE, and PB). After that, the amount of neurogranin mRNA in the cerebral neocortex decreased gradually until postnatal years 2-3. The in situ hybridization experiments also showed a transient increase of neurogranin mRNA in the neocortex during postnatal day 70 to postnatal month 6. The transient increase was prominent in layers II and III of areas FD and TE; deep in layer III of area PB; and in layers II, III, and IV of area OC. In the hippocampus, in contrast to the results in the neocortex, the expression of neurogranin mRNA was decreased almost continuously during the postnatal period. The transiently increased expression of neurogranin in the postnatal neocortex may be a molecular basis for the postsynaptic modification of afferent inputs possibly from subcortical structures.

Expression of protein kinase C-substrate mRNAs in the basal ganglia of adult and infant macaque monkeys

We performed in situ hybridization histochemistry on the monkey basal ganglia to investigate the mRNA localization of three protein kinase C substrates (GAP-43, MARCKS, and neurogranin), of which expression plays a role in structural changes in neurites and synapses. Weak hybridization signals for GAP-43 mRNA and intense signals for both MARCKS and neurogranin mRNAs were observed in the adult neostriatum. All three of the mRNAs were expressed in both substance P-positive direct pathway neurons and enkephalin-positive indirect pathway neurons. In the nucleus accumbens, the hybridization signals for the three mRNAs were weaker than those in the neostriatum. Double-label in situ hybridization histochemistry in the neostriatum revealed that GAP-43 and neurogranin mRNAs were expressed in a subset of MARCKS-positive neurons. While intense hybridization signals for MARCKS mRNA were observed in all of the other basal ganglia regions such as the globus pallidus, substantia innominata, subthalamic nucleus, and substantia nigra, intense signals for GAP-43 mRNA were restricted to the substantia innominata and substantia nigra pars compacta. No signal for neurogranin mRNA was observed in the basal ganglia regions outside the neostriatum and the nucleus accumbens. These results indicate that the protein kinase C substrates are abundant in some specific connections in cortico-basal ganglia circuits. Developmental analysis showed that the expression level in the putamen and nucleus accumbens, but not in the caudate nucleus, was higher in the infant than in the adult, suggesting that synaptic maturation in the caudate nucleus occurs earlier than that in the putamen and nucleus accumbens.

Developmental changes in the expression of growth-associated protein-43 mRNA in the monkey thalamus: northern blot and in situ hybridization studies

The expression of growth-associated protein-43 has been related to axonal elongation and synaptic sprouting. Using the Northern blot analysis, we investigated the developmental changes of growth-associated protein-43 mRNA in the thalamus of macaque monkeys. The amount of growth-associated protein-43 mRNA was high at embryonic day 125, and decreased at postnatal day 1. It increased again at postnatal day 8, reached its peak value at postnatal days 50-70, and then decreased gradually until postnatal year 1. We previously reported that the amount of growth-associated protein-43 mRNA in the cerebral cortex decreased roughly exponentially during perinatal and postnatal periods and that it approached the asymptote by postnatal day 70 [Oishi T, Higo N, Umino Y, Matsuda K, Hayashi M (1998) Development of GAP-43 mRNA in the macaque cerebral cortex. Dev Brain Res 109:87-97]. The present findings may indicate that extensive synaptic growth of thalamic neurons continues even after that of cortical neurons has finished. We then performed in situ hybridization to investigate whether the expression level of growth-associated protein-43 mRNA was different among various thalamic nuclei. In the infant thalamus (postnatal days 70-90), moderate to intense expression of growth-associated protein-43 mRNA was detected in all thalamic nuclei. Quantitative analysis in the infant thalamus indicated that the expression levels were different between the nuclear groups that are defined by the origin of their afferents. The expression in the first order nuclei, which receive their primary afferent fibers from ascending pathways [Guillery RW (1995) Anatomical evidence concerning the role of the thalamus in corticocortical communication: a brief review. J Anat 187 (Pt 3):583-592], was significantly higher than that in the higher order nuclei. While moderate expression was also detected in the adult dorsal thalamus, the expression in the first order nuclei was almost the same as that in the higher order nuclei. Thus, the in situ hybridization experiments indicated that the transient postnatal increase in the amount of growth-associated protein-43 mRNA, which was shown by the Northern blot analysis, was mainly attributed to enhanced expression in the first order nuclei during the postnatal period. This may be a molecular basis for environmentally induced modification of thalamocortical synapses.