Heterozygosity for Nuclear Factor One X in mice models features of Malan syndrome

PIN1 is a novel interaction partner and a negative upstream regulator of the transcription factor NFIB

NFIB is a transcription factor of the Nuclear Factor One (NFI) family that is essential for embryonic development. Post-translational control of NFIB or its upstream regulators have not been well characterized. Here, we show that PIN1 binds NFIB in a phosphorylation-dependent manner, via its WW domain. PIN1 interacts with the well-conserved N-terminal domains of all NFIs. Moreover, PIN1 attenuates the transcriptional activity of NFIB; this attenuation requires substrate binding by PIN1 but not its isomerase activity. Paradoxically, we found stabilization of NFIB by PIN1. We propose that PIN1 represses NFIB function not by regulating its abundance but by inducing a conformational change. These results identify NFIB as a novel PIN1 target and posit a role for PIN1 in post-translational regulation of NFIB and other NFIs.

A protocol for high-resolution episcopic microscopy and 3D volumetric analyses of the adult mouse brain

The rapid evolution of different imaging modalities in the last two decades has enabled the investigation of the role of different genes in development and disease to be studied in a range of model organisms. However, selection of the appropriate imaging technique depends on a number of constraints, including cost, time, image resolution, size of the sample, computational complexity and processing power. Here, we use the adult mouse central nervous system to investigate whether High-Resolution Episcopic Microscopy (HREM) can provide an effective means to study the volume of individual subregions within the brain. We find that HREM can provide precise volume quantification of different structures within the mouse brain, albeit with limitations regarding the time involved for analysis and the necessity of some estimations.

Early diagnosis of Malan syndrome in an infant presenting with macrocephaly

We present an infant with persistent macrocephaly and developmental delay. There is a wide range of differential diagnoses for this presentation, including many rare genetic conditions. Here, a diagnosis of Malan syndrome was made-a rare overgrowth syndrome caused by haploinsufficiency of NFIX and features affecting the neurological and musculoskeletal systems. Improvements in genomic medicine technologies and clinical services have revolutionised the way clinicians diagnose rare diseases. We highlight the importance of early genetic testing, particularly if there are red flag features such as developmental delay, and the need for a coordinated strategy to improve the management of rare diseases like Malan syndrome.

Hydrocephalus in Nfix−/− Mice Is Underpinned by Changes in Ependymal Cell Physiology

Nuclear factor one X (NFIX) is a transcription factor required for normal ependymal development. Constitutive loss of Nfix in mice (Nfix−/−) is associated with hydrocephalus and sloughing of the dorsal ependyma within the lateral ventricles. Previous studies have implicated NFIX in the transcriptional regulation of genes encoding for factors essential to ependymal development. However, the cellular and molecular mechanisms underpinning hydrocephalus in Nfix−/− mice are unknown. To investigate the role of NFIX in hydrocephalus, we examined ependymal cells in brains from postnatal Nfix−/− and control (Nfix+/+) mice using a combination of confocal and electron microscopy. This revealed that the ependymal cells in Nfix−/− mice exhibited abnormal cilia structure and disrupted localisation of adhesion proteins. Furthermore, we modelled ependymal cell adhesion using epithelial cell culture and revealed changes in extracellular matrix and adherens junction gene expression following knockdown of NFIX. Finally, the ablation of Nfix from ependymal cells in the adult brain using a conditional approach culminated in enlarged ventricles, sloughing of ependymal cells from the lateral ventricles and abnormal localisation of adhesion proteins, which are phenotypes observed during development. Collectively, these data demonstrate a pivotal role for NFIX in the regulation of cell adhesion within ependymal cells of the lateral ventricles.

Perineuronal net abnormalities in Slc13a4+/- mice are rescued by postnatal administration of N-acetylcysteine

Disruptions to either sulfate supply or sulfation enzymes can affect brain development and have long-lasting effects on brain function, yet our understanding of the molecular mechanisms governing this are incomplete. Perineuronal nets (PNNs) are highly sulfated, specialized extracellular matrix structures that regulate the maturation of synaptic connections and neuronal plasticity. We have previously shown that mice heterozygous for the brain sulfate transporter Slc13a4 have abnormal social interactions, memory, exploratory behaviors, stress and anxiety of postnatal origin, pointing to potential deficits in PNN biology, and implicate SLC13A4 as a critical factor required for regulating normal synaptic connectivity and function. Here, we sought to investigate aberrant PNN formation as a potential mechanism contributing to the functional deficits displayed by Slc13a4^+/- mice. Following social interactions, we reveal reduced neuronal activation in the somatosensory cortex of Slc13a4^+/- mice, and altered inhibitory and excitatory postsynaptic currents. In line with this, we found a reduction in parvalbumin-expressing neurons decorated with PNNs, as well as reduced expression of markers for PNN maturation. Finally, we reveal that postnatal administration of N-acetylcysteine prevented PNN abnormalities from manifesting in Slc13a4^+/- adult animals. Collectively, these data highlight a central role for postnatal SLC13A4 in normal PNN formation, circuit function and subsequent animal behavior.

Expression of NFIA and NFIB within the murine spinal cord

The Nuclear factor I proteins comprise a family of transcription factors that are expressed in many developing and mature cell populations, including within the central nervous system. Within the embryonic mouse spinal cord, NFIA and NFIB are expressed by neural progenitor cells lining the central canal, where they act to promote astrocytic and oligodendrocytic lineage specification. Cells lining the mature spinal cord central canal retain characteristics of neural progenitor cells, but the expression of NFIA and NFIB within the mature spinal cord at a cell-type-specific level remains undefined. Here, we investigated where these two transcription factors are expressed within the adult mouse spinal cord. We reveal that both factors are expressed in similar cohorts of mature cells, including ependymal cells, interneurons and motor neurons. We also show robust and widespread expression of NFIA and NFIB within nestin-expressing cells following injury to the spinal cord. Collectively, these data provide a basis to further define what functional role(s) NFIA and NFIB play within the adult spinal cord.

Investigating cortical features of Sotos syndrome using mice heterozygous for Nsd1

Sotos syndrome is a developmental disorder characterized by a suite of clinical features. In children, the three cardinal features of Sotos syndrome are a characteristic facial appearance, learning disability and overgrowth (height and/or head circumference > 2 SDs above average). These features are also evident in adults with this syndrome. Over 90% of Sotos syndrome patients are haploinsufficient for the gene encoding nuclear receptor-binding Su(var)3-9, Enhancer-of-zesteand Trithorax domain-containing protein 1 (NSD1). NSD1 is a histone methyltransferase that catalyzes the methylation of lysine residue 36 on histone H3. However, although the symptomology of Sotos syndrome is well established, many aspects of NSD1 biology remain unknown. Here, we assessed the expression of Nsd1 within the mouse brain, and showed a predominantly neuronal pattern of expression for this histone-modifying factor. We also generated a mouse strain lacking one allele of Nsd1 and analyzed morphological and behavioral characteristics in these mice, showing behavioral characteristics reminiscent of some of the deficits seen in Sotos syndrome patients.

A simple, web-based repository for the management, access and analysis of micrographic images

Microscopy is advancing at a rapid pace, enabling high-speed, high-resolution analyses to be conducted in a wide range of cellular contexts. For example, the capacity to quickly capture high-resolution images from multiple optical sections over multiple channels with confocal microscopy has allowed researchers to gain deeper understanding of tissue morphology via techniques such as three-dimensional rendering, as have more recent advances such as lattice light sheet microscopy and superresolution structured illumination microscopy. With this, though, comes the challenge of storing, curating, analysing and sharing data. While there are ways in which this has been attempted previously, few approaches have provided a central repository in which all of these different aspects of microscopy can be seamlessly integrated. Here, we describe a web-based storage and analysis platform called Microndata, that enables relatively straightforward storage, annotation, tracking, analysis and multi-user access to micrographs. This easy to use tool will simplify and harmonise laboratory work flows, and, importantly, will provide a central storage repository that is readily accessed, even after the researcher responsible for capturing the images has left the laboratory. Microndata is open-source software, available at http://www.microndata.net/.