Brain Symptoms of Tuberous Sclerosis Complex: Pathogenesis and Treatment.

The mammalian target of the rapamycin (mTOR) system plays multiple, important roles in the brain, regulating both morphology, such as cellular size, shape, and position, and function, such as learning, memory, and social interaction. Tuberous sclerosis complex (TSC) is a congenital disorder caused by a defective suppressor of the mTOR system, the TSC1/TSC2 complex. Almost all brain symptoms of TSC are manifestations of an excessive activity of the mTOR system. Many children with TSC are afflicted by intractable epilepsy, intellectual disability, and/or autism. In the brains of infants with TSC, a vicious cycle of epileptic encephalopathy is formed by mTOR hyperactivity, abnormal synaptic structure/function, and excessive epileptic discharges, further worsening epilepsy and intellectual/behavioral disorders. Molecular target therapy with mTOR inhibitors has recently been proved to be efficacious for epilepsy in human TSC patients, and for autism in TSC model mice, indicating the possibility for pharmacological treatment of developmental synaptic disorders.

Three human ARX mutations cause the lissencephaly-like and mental retardation with epilepsy-like pleiotropic phenotypes in mice.

ARX (the aristaless-related homeobox gene) is a transcription factor that participates in the development of GABAergic and cholinergic neurons in the forebrain. Many ARX mutations have been identified in X-linked lissencephaly and mental retardation with epilepsy, and thus ARX is considered to be a causal gene for the two syndromes although the neurobiological functions of each mutation remain unclear. We attempted to elucidate the causal relationships between individual ARX mutations and disease phenotypes by generating a series of mutant mice. We generated three types of mice with knocked-in ARX mutations associated with X-linked lissencephaly (P353R) and mental retardation [P353L and 333ins(GCG)7]. Mice with the P355R mutation (equivalent to the human 353 position) that died after birth were significantly different in Arx transcript/protein amounts, GABAergic and cholinergic neuronal development, brain morphology and lifespan from mice with P355L and 330ins(GCG)7 but considerably similar to Arx-deficient mice with truncated ARX mutation in lissencephaly. Mice with the 330ins(GCG)7 mutation showed severe seizures and impaired learning performance, whereas mice with the P355L mutation exhibited mild seizures and only slightly impaired learning performance. Both types of mutant mice exhibited the mutation-specific lesser presence of GABAergic and cholinergic neurons in the striatum, medial septum and ventral forebrain nuclei when compared with wild-type mice. Present findings that reveal a causal relationship between ARX mutations and the pleiotropic phenotype in mice, suggest that the ARX-related syndrome, including lissencephaly or mental retardation, is caused by only the concerned ARX mutations without the involvement of other genetic factors.

Correlation between unconjugated bilirubin and total cholesterol in the sera of 1-month-old infants.

AIM: To investigate why breastfed infants are more likely to have prolonged jaundice than formula-fed infants. METHODS: Serum unconjugated bilirubin (UCB), total cholesterol (TC) and triglyceride (TG) were measured for 102 infants of 1 month. Enrolled infants were 42 breastfed, 40 mixed-fed and 20 bottle-fed infants. Statistic analyses for relationship among UCB, TC, TG, perinatal factors and post-natal factors were performed for these infants. RESULTS: In correlation analyses UCB was correlated with peak transcutaneous bilirubin value in neonatal period (TcBn) (r = 0.612, P < 0.0001) and with TC (r = 0.383, P < 0.0001). When analyses of covariance (ANCOVA) for UCB were performed using TcBn as the covariate, the results indicated that there was neither significant main nor interaction effect of feeding method on UCB, and that main and interaction effects of TC on UCB were significant when TC was categorised into two groups (≤150 mg/dL and >150 mg/dL). CONCLUSIONS: It is suggested that both neonatal hyperbilirubinemia and subsequent higher plasma TC are associated factors for prolonged jaundice.

Aristaless-related homeobox gene disruption leads to abnormal distribution of GABAergic interneurons in human neocortex: evidence based on a case of X-linked lissencephaly with abnormal genitalia (XLAG).

X-linked lissencephaly with abnormal genitalia (XLAG) is a rare disorder caused by mutations in the aristaless-related homeobox (ARX) gene, located on Xp22.13. Arx-null mice show loss of tangential migration of GABAergic interneurons, presumably being related to caudal ganglionic eminence tangential migration. In the present study, we investigated a subpopulation of GABAergic interneurons in the brain of an infant with XLAG, who had a novel nonsense mutation of the ARX gene, compared with those of age-matched normal controls and Miller-Dieker syndrome. We performed immunocytochemistry for interneuron and migration markers. We found that glutamic acid decarboxylase (GAD)- and calretinin (CR)-containing cells were significantly reduced in the neocortex and located in the white matter and neocortical subventricular zone, while neuropeptide Y- or cholecystokinin-containing cells were normally distributed. Moreover, in the neocortical subventricular region, the GAD- and CR-containing cells expressed the radial migration marker Mash-1 as well as nestin. Our findings suggest that ARX protein controls not only the tangential migration of GABAergic interneurons from the ganglionic eminence, but also may serve to induce radial migration from the neocortical subventricular zone.

Familial reducing body myopathy.

Reducing body myopathy (RBM) is a rare pathologically defined myopathy characterized by the presence of inclusion bodies which are abnormally stained by menadione-nitroblue-tetrazolium. The clinical symptoms vary widely as to the age of onset, disease progression and severity. Among the many reported patients, there have been only three families with this disorder, showing a manifold of clinicopathological features in each family. We report a fourth family with RBM affecting a boy and his mother. The proband (boy) began to have difficulty putting on his trousers at age 10years and difficulty arising from a chair at 11years. His spine was rigid. His mother, on the other hand, noticed foot-drop at the age 29, but the clinical course was rapidly progressive, and she was wheelchair-bound at 34years. Both patients had generalized muscle weakness and atrophy and with mild CK elevation. Muscle pathology was characterized by the presence of atrophic fibers with reducing bodies in some areas. As these patients demonstrate, clinical symptoms in RBM are very variable, even within the same family. There are no specific clinical characteristics distinctive to RBM, thus further studies are necessary to characterize this disorder both clinically and pathologically.

People with absolute pitch process tones with producing P300.

We recorded a P300 component of event-related potentials associated with auditory oddball tasks in nine absolute pitch (AP) possessors and seven non-AP possessors. The previous studies demonstrated that AP possessors did not appear to employ working memory during auditory oddball tasks because they have a fixed tonal template in their memories. However, the present findings showed that the AP possessors exhibited similar P300 as the non-AP possessors and did update the tonal context in the auditory oddball tasks. This result suggests that the AP possessors do not always refer to the fixed tonal template in their memories when executing the oddball tasks and they employ working memory properly according to the difficulty of the auditory tasks.

TSC1 controls distribution of actin fibers through its effect on function of Rho family of small GTPases and regulates cell migration and polarity.

The tumor-suppressor genes TSC1 and TSC2 are mutated in tuberous sclerosis, an autosomal dominant multisystem disorder. The gene products of TSC1 and TSC2 form a protein complex that inhibits the signaling of the mammalian target of rapamycin complex1 (mTORC1) pathway. mTORC1 is a crucial molecule in the regulation of cell growth, proliferation and survival. When the TSC1/TSC2 complex is not functional, uncontrolled mTORC1 activity accelerates the cell cycle and triggers tumorigenesis. Recent studies have suggested that TSC1 and TSC2 also regulate the activities of Rac1 and Rho, members of the Rho family of small GTPases, and thereby influence the ensuing actin cytoskeletal organization at focal adhesions. However, how TSC1 contributes to the establishment of cell polarity is not well understood. Here, the relationship between TSC1 and the formation of the actin cytoskeleton was analyzed in stable TSC1-expressing cell lines originally established from a Tsc1-deficient mouse renal tumor cell line. Our analyses showed that cell proliferation and migration were suppressed when TSC1 was expressed. Rac1 activity in these cells was also decreased as was formation of lamellipodia and filopodia. Furthermore, the number of basal actin stress fibers was reduced; by contrast, apical actin fibers, originating at the level of the tight junction formed a network in TSC1-expressing cells. Treatment with Rho-kinase (ROCK) inhibitor diminished the number of apical actin fibers, but rapamycin had no effect. Thus, the actin fibers were regulated by the Rho-ROCK pathway independently of mTOR. In addition, apical actin fibers appeared in TSC1-deficient cells after inhibition of Rac1 activity. These results suggest that TSC1 regulates cell polarity-associated formation of actin fibers through the spatial regulation of Rho family of small GTPases.

Tuberin activates and controls the distribution of Rac1 via association with p62 and ubiquitin through the mTORC1 signaling pathway.

Recent studies indicated that the tuberous sclerosis 2 (TSC2) gene product, tuberin, regulates Rac1 activity. However, the underlying mechanism by which tuberin regulates Rac1 activity has not been clearly elucidated to date. To better understand the molecular link between tuberin function and Rac1, we characterized the activity and distribution of Rac1 in mouse Tsc2-deficient renal tumor cells using restoration experiments with wild-type tuberin. Rac1 activity was significantly higher in tuberin-expressing cells compared with control Tsc2-deficient cells. Further, Rac1 activation was induced by rapamycin treatment or knockdown of raptor, but not rictor, in Tsc2-deficient cells, indicating that mTORC1 is an upstream negative regulator of Rac1. Intriguingly, Rac1 appeared to form cytoplasmic dots in Tsc2-deficient cells, but not in tuberin-expressing and since rapamycin treatment dispersed these dots, involvement of aberrant mTOR complex 1 (mTORC1) activation in the dot formation was suspected. Moreover, the dots were co-localized with p62/sequestosome-1 and ubiquitin. These findings imply that Rac1 distribution and/or its degradation may be regulated by tuberin through the mTORC1 signaling pathway.

Progressive leukoencephalopathy associated with aluminum deposits in myelin sheath.

A 20-year-old woman with progressive leukoencephalopathy developed mental and motor disabilities and fell into a coma after suffering head trauma and febrile episodes from infancy. Brain imaging showed massive abnormal signals in the white matter. The electron spectroscopic imaging of biopsied brain tissue confirmed the electron-dense deposits to be associated with aluminum accumulation in the myelin sheath. Her brain pathology, which showed ferritin- and naphtochrome green-positive deposits, supported the imaging analysis. The clinicopathological features indicate a new form of progressive leukoencephalopathy.

Unfolded protein response and aggresome formation in hereditary reducing-body myopathy.

Reducing-body myopathy (RBM) is a rare myopathy characterized by the presence of unique sarcoplasmic inclusions called reducing bodies (RBs). We characterized the aggresomal features of RBs that contained gamma-tubulin, ubiquitin, and endoplasmic reticulum (ER) chaperones, together with a set of membrane proteins, in a family with hereditary RBM. Increased messenger ribonucleic acid and protein levels of a molecular chaperone, glucose-related protein 78, were also observed. These results suggest that the unfolded protein response caused by the accumulation of misfolded proteins in the endoplasmic reticulum plays an important role in the formation of RBs.