Reprogramming of the epigenome in neurodevelopmental disorders

The etiology of neurodevelopmental disorders (NDDs) remains a challenge for researchers. Human brain development is tightly regulated and sensitive to cellular alterations caused by endogenous or exogenous factors. Intriguingly, the surge of clinical sequencing studies has revealed that many of these disorders are monogenic and monoallelic. Notably, chromatin regulation has emerged as highly dysregulated in NDDs, with many syndromes demonstrating phenotypic overlap, such as intellectual disabilities, with one another. Here we discuss epigenetic writers, erasers, readers, remodelers, and even histones mutated in NDD patients, predicted to affect gene regulation. Moreover, this review focuses on disorders associated with mutations in enzymes involved in histone acetylation and methylation, and it highlights syndromes involving chromatin remodeling complexes. Finally, we explore recently discovered histone germline mutations and their pathogenic outcome on neurological function. Epigenetic regulators are mutated at every level of chromatin organization. Throughout this review, we discuss mechanistic investigations, as well as various animal and iPSC models of these disorders and their usefulness in determining pathomechanism and potential therapeutics. Understanding the mechanism of these mutations will illuminate common pathways between disorders. Ultimately, classifying these disorders based on their effects on the epigenome will not only aid in prognosis in patients but will aid in understanding the role of epigenetic machinery throughout neurodevelopment.

What is "special" about face perception?

There is growing evidence that face recognition is "special" but less certainty concerning the way in which it is special. The authors review and compare previous proposals and their own more recent hypothesis, that faces are recognized "holistically" (i.e., using relatively less part decomposition than other types of objects). This hypothesis, which can account for a variety of data from experiments on face memory, was tested with 4 new experiments on face perception. A selective attention paradigm and a masking paradigm were used to compare the perception of faces with the perception of inverted faces, words, and houses. Evidence was found of relatively less part-based shape representation for faces. The literatures on machine vision and single unit recording in monkey temporal cortex are also reviewed for converging evidence on face representation. The neuropsychological literature is reviewed for-evidence on the question of whether face representation differs in degree or kind from the representation of other types of objects.

The inverted face inversion effect in prosopagnosia: evidence for mandatory, face-specific perceptual mechanisms

Does the human visual system contain a specialized system for face recognition, not used for the recognition of other objects? This question was addressed using the "face inversion effect" which refers to the loss of our normal proficiency at face perception when faces are inverted. We found that a prosopagnosic subject paradoxically performed better at matching inverted faces than upright faces, the opposite of the normal "face inversion effect". The fact that his impairment was most pronounced with the stimuli for which normal subjects show the greatest proficiency in face perception provides evidence of a neurologically localized module for upright face recognition in humans. An additional implication of these data is that specialized systems may control behavior even when they are malfunctioning and therefore maladeaptive, consistent with the mandatory operation of such systems according to the "modularity" hypothesis of the cognitive architecture.

Editing of Trypanosoma brucei maxicircle CR5 mRNA generates variable carboxy terminal predicted protein sequences

RNA editing post-transcriptionally modifies several mRNAs from the maxicircle of kinetoplastid parasites by addition and removal of uridine residues. We report here that maxicircle CR5 transcripts of Trypanosoma brucei are edited in two domains separated by an eight nucleotide sequence that remains unedited. The large 5' domain is edited to a consensus sequence while the smaller 3' domain is edited to multiple final sequences. In all, 205-217 Us are inserted and 13-16 encoded uridines are deleted from the CR5 mRNA, producing a mature transcript 75-80% larger than the unedited transcript. The edited RNAs predict small, highly hydrophobic proteins. The carboxy terminal 15-30% of these predicted proteins have multiple different amino acid sequences as a result of the variable edited 3' mRNA sequence, but these fall into two families of sequence. Limited amino acid sequence and hydrophobicity profile similarities suggest that the protein encoded by edited CR5 mRNA may be a subunit of NADH dehydrogenase.

Comparison of sufentanil and enflurane-nitrous oxide anesthesia for myocardial revascularization

This study compared the stress response in patients with coronary artery disease undergoing myocardial revascularization anesthetized with either sufentanil and oxygen or enflurane-nitrous oxide and oxygen. Throughout induction and maintenance of anesthesia, and while the patients were in the intensive care unit, hemodynamics plus plasma catecholamine, sufentanil, and enflurane concentrations were recorded and compared. Three groups were studied: sufentanil, 15 micrograms/kg at induction; sufentanil, 15 micrograms/kg at induction plus 10 micrograms/kg on initiation of cardiopulmonary bypass (CPB); and enflurane anesthesia. Hemodynamics were remarkably stable in all groups but required considerable fine tuning when enflurane was administered. The "stress" of CPB was blunted by the additional dose of sufentanil, as well as by enflurane. This was reflected in those patients receiving the extra sufentanil or enflurane by less severe increases in their epinephrine or norepinephrine concentrations and by less frequent use of sodium nitroprusside to control mean arterial pressure compared to the group of patients given the lower-dose sufentanil. This study suggests that higher blood levels of sufentanil can attenuate, but not eliminate, the stress response to CPB, as can enflurane, and that both the narcotic and inhalation anesthetic techniques for patients with coronary artery disease were quite satisfactory.

Ascending myeloencephalopathy due to intrathecal vincristine sulfate. A fatal chemotherapeutic error

A case of fatal myeloencephalopathy secondary to accidental intrathecal administration of vincristine is reported in a 16-year-old boy. He underwent a progressive ascending chemical meningoencephalitis leading to coma, and died 36 days after the injection. Multiple samples of cerebrospinal fluid (CSF) and serum were assayed for vincristine sulfate. CSF levels of vincristine were consistently much higher than serum levels. At autopsy, all regions of the brain that had been in direct contact with the CSF were necrotic. The spinal cord was likewise necrotic throughout its length. Microscopically there was total neuronal loss with tissue destruction in the affected regions. The presence of numerous gemistocytic astrocytes, some in arrested mitosis, was a conspicuous feature in these areas. Three previous reports of intrathecal vincristine instillation are reviewed. No treatment for this devastating iatrogenic error exists, underscoring the importance of preventive measures in chemotherapy administration.