Novel MECP2 gene therapy is effective in a multicenter study using two mouse models of Rett syndrome and is safe in non-human primates.

The AAV9 gene therapy vector presented in this study is safe in mice and non-human primates and highly efficacious without causing overexpression toxicity, a major challenge for clinical translation of Rett syndrome gene therapy vectors to date. Our team designed a new truncated methyl-CpG-binding protein 2 (MECP2) promoter allowing widespread expression of MECP2 in mice and non-human primates after a single injection into the cerebrospinal fluid without causing overexpression symptoms up to 18 months after injection. Additionally, this new vector is highly efficacious at lower doses compared with previous constructs as demonstrated in extensive efficacy studies performed by two independent laboratories in two different Rett syndrome mouse models carrying either a knockout or one of the most frequent human mutations of Mecp2. Overall, data from this multicenter study highlight the efficacy and safety of this gene therapy construct, making it a promising candidate for first-in-human studies to treat Rett syndrome.

Infantile metastatic ependymoma with a novel molecular profile and favorable outcome to intensive chemotherapy without irradiation: Case-based review.

Ependymal tumors are the third most common brain tumor under 14 years old. Even though metastatic disease is a rare event, it affects mostly young children and carries an adverse prognosis. The factors associated with dissemination and the best treatment approach have not yet been established and there is limited published data on how to manage metastatic disease, especially in patients under 3 years of age. We provide a review of the literature on clinical characteristics and radiation-sparing treatments for metastatic ependymoma in children under 3 years of age treated. The majority (73%) of the identified cases were above 12 months old and had the PF as the primary site at diagnosis. Chemotherapy-based approaches, in different regimens, were used with radiation reserved for progression or relapse. The prognosis varied among the studies, with an average of 50%-58% overall survival. This study also describes the case of a 7-month-old boy with metastatic posterior fossa (PF) ependymoma, for whom we identified a novel SPECC1L-RAF1 gene fusion using a patient-centric comprehensive molecular profiling protocol. The patient was successfully treated with intensive induction chemotherapy followed by high-dose chemotherapy and autologous hematopoietic progenitor cell rescue (AuHSCR). Currently, the patient is in continuous remission 5 years after his diagnosis, without radiation therapy. The understanding of the available therapeutic approaches may assist physicians in their management of such patients. This report also opens the perspective of newly identified molecular alterations in metastatic ependymomas that might drive more chemo-sensitive tumors.

Detection of brain somatic variation in epilepsy-associated developmental lesions.

OBJECTIVE: Epilepsy-associated developmental lesions, including malformations of cortical development and low-grade developmental tumors, represent a major cause of drug-resistant seizures requiring surgical intervention in children. Brain-restricted somatic mosaicism has been implicated in the genetic etiology of these lesions; however, many contributory genes remain unidentified. METHODS: We enrolled 50 children who were undergoing epilepsy surgery into a translational research study. Resected tissue was divided for clinical neuropathologic evaluation and genomic analysis. We performed exome and RNA sequencing to identify somatic variation and we confirmed our findings using high-depth targeted DNA sequencing. RESULTS: We uncovered candidate disease-causing somatic variation affecting 28 patients (56%), as well as candidate germline variants affecting 4 patients (8%). In agreement with previous studies, we identified somatic variation affecting solute carrier family 35 member A2 (SLC35A2) and mechanistic target of rapamycin kinase (MTOR) pathway genes in patients with focal cortical dysplasia. Somatic gains of chromosome 1q were detected in 30% (3 of 10) of patients with Type I focal cortical dysplasia (FCD)s. Somatic variation in mitogen-activated protein kinase (MAPK) pathway genes (i.e., fibroblast growth factor receptor 1 [FGFR1], FGFR2, B-raf proto-oncogene, serine/threonine kinase [BRAF], and KRAS proto-oncogene, GTPase [KRAS]) was associated with low-grade epilepsy-associated developmental tumors. RNA sequencing enabled the detection of somatic structural variation that would have otherwise been missed, and which accounted for more than one-half of epilepsy-associated tumor diagnoses. Sampling across multiple anatomic regions revealed that somatic variant allele fractions vary widely within epileptogenic tissue. Finally, we identified putative disease-causing variants in genes not yet associated with focal cortical dysplasia. SIGNIFICANCE: These results further elucidate the genetic basis of structural brain abnormalities leading to focal epilepsy in children and point to new candidate disease genes.

PTEN somatic mutations contribute to spectrum of cerebral overgrowth.

Phosphatase and tensin homologue (PTEN) regulates cell growth and survival through inhibition of the mammalian target of rapamycin (MTOR) signalling pathway. Germline genetic variation of PTEN is associated with autism, macrocephaly and PTEN hamartoma tumour syndromes. The effect of developmental PTEN somatic mutations on nervous system phenotypes is not well understood, although brain somatic mosaicism of MTOR pathway genes is an emerging cause of cortical dysplasia and epilepsy in the paediatric population. Here we report two somatic variants of PTEN affecting a single patient presenting with intractable epilepsy and hemimegalencephaly that varied in clinical severity throughout the left cerebral hemisphere. High-throughput sequencing analysis of affected brain tissue identified two somatic variants in PTEN. The first variant was present in multiple cell lineages throughout the entire hemisphere and associated with mild cerebral overgrowth. The second variant was restricted to posterior brain regions and affected the opposite PTEN allele, resulting in a segmental region of more severe malformation, and the only neurons in which it was found by single-nuclei RNA-sequencing had a unique disease-related expression profile. This study reveals brain mosaicism of PTEN as a disease mechanism of hemimegalencephaly and furthermore demonstrates the varying effects of single- or bi-allelic disruption of PTEN on cortical phenotypes.

Submucosal Nerve Diameter in the Rectum Increases With Age: An Important Consideration for the Diagnosis of Hirschsprung Disease.

INTRODUCTION: Hypertrophic submucosal nerves, defined as ≥40 µm in diameter, are considered supportive of a diagnosis of HSCR, but the effect of age on nerve diameter has not been well-studied. We sought to determine the distribution of the largest nerve diameter in ganglionic rectal biopsies and the significance of hypertrophic submucosal nerves in the diagnosis of Hirschsprung disease (HSCR) based on age. METHODS: Rectal biopsies performed in the evaluation of HSCR were retrospectively reviewed from 179 patients (151 ganglionic biopsies, 28 aganglionic biopsies), and the diameter of the largest submucosal nerve was measured. RESULTS: In non-Hirschsprung disease (non-HSCR) biopsies, submucosal nerve diameter increased with age. In patients <1 year, the average diameter was 34.1 ± 11.6 µm but increased to 50.8 ± 17.3 µm after 1 year of age. Submucosal nerves ≥40 µm in diameter were significantly associated with HSCR across all ages [HSCR = 25/28 (89.3%) vs non-HSCR = 59/151 (39.1%), p < 0.0001] and remained significant in patients <1 year of age [HSCR = 22/24 (91.7%) vs non-HSCR = 19/91 (20.9%), p < 0.0001]. CONCLUSIONS: The diameter of submucosal nerves increases with age, and ≥40 µm nerves are common after 1 year of age.

SPEG-deficient skeletal muscles exhibit abnormal triad and defective calcium handling.

Centronuclear myopathies (CNM) are a subtype of congenital myopathies (CM) characterized by skeletal muscle weakness and an increase in the number of central myonuclei. We have previously identified three CNM probands, two with associated dilated cardiomyopathy, carrying striated preferentially expressed gene (SPEG) mutations. Currently, the role of SPEG in skeletal muscle function is unclear as constitutive SPEG-deficient mice developed severe dilated cardiomyopathy and died in utero. We have generated a conditional Speg-KO mouse model and excised Speg by crosses with striated muscle-specific cre-expressing mice (MCK-Cre). The resulting litters had a delay in Speg excision consistent with cre expression starting in early postnatal life and, therefore, an extended lifespan up to a few months. KO mice were significantly smaller and weaker than their littermate-matched controls. Histopathological skeletal muscle analysis revealed smaller myofibers, marked fiber-size variability, and poor integrity and low number of triads. Further, SPEG-deficient muscle fibers were weaker by physiological and in vitro studies and exhibited abnormal Ca2+ handling and excitation-contraction (E-C) coupling. Overall, SPEG deficiency in skeletal muscle is associated with fewer and abnormal triads, and defective calcium handling and excitation-contraction coupling, suggesting that therapies targeting calcium signaling may be beneficial in such patients.

Neuropathology of Mowat-Wilson Syndrome.

Mowat-Wilson syndrome (MWS) is a syndromic form of Hirschsprung disease that is characterized by variable degrees of intellectual disability, characteristic facial dysmorphism, and a diverse set of other congenital malformations due to haploinsufficiency of ZEB2. A variety of brain malformations have been described in neuroimaging studies of MWS patients, and the role of ZEB2 in the brain has been studied in a multitude of genetically engineered mouse models that are now available. However, a paucity of autopsy information limits our ability to correlate data from neuroimaging studies and animal models with actual MWS patient tissues. Here, we report the autopsy neuropathology of a 19-year-old male patient with MWS. Autopsy neuropathology findings correlated well with the reported MWS neuroimaging data and are in keeping with data from genetically engineered MWS mouse models. This autopsy enhances our understanding of ZEB2 function in human brain development and demonstrates the reliability of MWS murine models.

Mentors' perspectives on the successes and challenges of mentoring in the COG Young Investigator mentorship program: A report from the Children's Oncology Group.

BACKGROUND: Identification and development of young investigators (YI) is critical to the long-term success of research organizations. In 2004, the Children's Oncology Group (COG) created a mentorship program to foster the career development of YIs (faculty <10 years from initial appointment). This study sought to assess mentors' long-term assessment of this program. PROCEDURE: In 2018, 101 past or current mentors in the COG YI mentorship program completed an online survey. Statistical comparisons were made with the Kruskal-Walis test. RESULTS: The response rate was 74.2%. As some mentors had multiple mentees, we report on 138 total mentee-mentor pairs. Mentors were 57.4% male, and mentees were 39.1% male. Mentors rated being mentored as a YI as important with a median rating of 90 on a scale of 1-100, interquartile range (IQR) 80-100. Most mentors reported that being mentored themselves helped their own success within COG (78.2%) and with their overall career development (92.1%). Most mentors enjoyed serving in the program (72.3%) and the median success rating (on a scale of 1-100) across the mentor-mentee pairings was 75, IQR 39-90. Success ratings did not differ by mentor/mentee gender, but improved with increased frequency of mentor-mentee interactions (P < .001). Mentor-mentee pairs who set initial goals reported higher success ratings than those who did not (P < .001). Tangible successes included current mentee COG committee involvement (45.7%), ongoing mentor-mentee collaboration (53.6%), and co-authored manuscript publication (38.4%). CONCLUSION: These data indicate that mentorship is important for successful professional development. Long-term mentoring success improves when mentors and mentees set goals upfront and meet frequently.

Long-term evidence that a pediatric oncology mentorship program for young investigators is feasible and beneficial in the cooperative group setting: A report from the Children's Oncology Group.

BACKGROUND: Mentorship of junior faculty is an integral component of career development. The Children's Oncology Group (COG) Young Investigator (YI) Committee designed a mentorship program in 2004 whose purpose was to pair YIs (faculty ≤10 years of first academic appointment) with a senior mentor to assist with career development and involvement in COG research activities. This study reports on the committee's ability to achieve these goals. PROCEDURE: An online survey was sent to YIs who were registered with the program from 2004 to2015, assessing three major domains: (1) overall experience with the mentor pairing, (2) satisfaction with the program, and (3) academic accomplishments of the mentees. RESULTS: The response rate was 64% (110/171). Overall, YIs rated the success of their mentorship pairing as 7.2 out of 10 (median) (25th, 75th quartile 3.6, 9.6). The direct effects of the mentorship program included 70% YIs reporting a positive effect on their career, 40% reporting any grant or manuscript resulting from the pairing, 47% forming a new research collaboration, and 43% receiving appointment to a COG committee. Respondents reported success in COG with 38% authoring a manuscript on behalf of COG and 65% reporting a leadership position including seven current or past COG discipline chairs and 20 study chairs. Finally, 74% of respondents said they would consider serving as mentors in the program in the future. CONCLUSION: The COG YI mentorship program has been well received by the majority of the participants and has helped to identify and train many current leaders in COG.

Intraocular Medulloepithelioma: AIRP Best Cases in Radiologic-Pathologic Correlation.

Editor's Note.-RadioGraphics continues to publish radiologic-pathologic case material selected from the American Institute for Radiologic Pathology (AIRP) "best case" presentations. The AIRP conducts a 4-week Radiologic Pathology Correlation Course, which is offered five times per year. On the penultimate day of the course, the best case presentation is held at the American Film Institute Silver Theater and Cultural Center in Silver Spring, Md. The AIRP faculty identifies the best cases, from each organ system, brought by the resident attendees. One or more of the best cases from each of the five courses are then solicited for publication in RadioGraphics. These cases emphasize the importance of radiologic-pathologic correlation in the imaging evaluation and diagnosis of diseases encountered at the institute and its predecessor, the Armed Forces Institute of Pathology (AFIP).

Hepcidin, an Iron Regulatory Hormone of Innate Immunity, is Differentially Expressed in Premature Fetuses with Early-Onset Neonatal Sepsis.

OBJECTIVE: Hepcidin, a mediator of innate immunity, binds the iron exporter ferroportin, leading to functional hypoferremia through intracellular iron sequestration. We explored hepcidin-ferroportin interactions in neonates clinically diagnosed with early-onset neonatal sepsis (EONS). STUDY DESIGN: Hepcidin and interleukin (IL)-6 were quantified by enzyme-linked immunosorbent assay (ELISA) in 92 paired cord blood-maternal blood samples in the following groups: "Yes" EONS (n = 41, gestational age [GA] 29 ± 1 weeks) and "No" EONS (n = 51, GA 26 ± 1 weeks). Placental hepcidin and ferroportin expression were evaluated by immunohistochemistry and real-time-polymerase chain reaction (RT-PCR). Liver hepcidin and ferroportin expression patterns were ascertained in autopsy specimens of neonates (n = 8) who died secondary to culture-proven sepsis. RESULTS: Cord blood hepcidin was significantly elevated (GA corrected, p = 0.018) and was positively correlated with IL-6 (r = 0.379, p = 0.001) in EONS. Hepcidin localized at syncytiotrophoblast and fetal vascular endothelium. Placental ferroportin, but not hepcidin mRNA correlated with cord blood hepcidin levels (r = 0.46, p = 0.039) and funisitis severity (r = 0.50, p = 0.018). Newborns who died from sepsis (n = 4) had higher hepatic hepcidin and iron sequestration, but lower ferroportin staining than those who died of nonsepsis causes (n = 4). CONCLUSION: Premature fetuses with EONS have elevated circulating hepcidin, likely related to lower placenta and liver ferroportin expression. Fetal hepcidin-ferroportin interaction appears to play a role in EONS pathophysiology independent of maternal response to intrauterine inflammation.

SPEG interacts with myotubularin, and its deficiency causes centronuclear myopathy with dilated cardiomyopathy.

Centronuclear myopathies (CNMs) are characterized by muscle weakness and increased numbers of central nuclei within myofibers. X-linked myotubular myopathy, the most common severe form of CNM, is caused by mutations in MTM1, encoding myotubularin (MTM1), a lipid phosphatase. To increase our understanding of MTM1 function, we conducted a yeast two-hybrid screen to identify MTM1-interacting proteins. Striated muscle preferentially expressed protein kinase (SPEG), the product of SPEG complex locus (SPEG), was identified as an MTM1-interacting protein, confirmed by immunoprecipitation and immunofluorescence studies. SPEG knockout has been previously associated with severe dilated cardiomyopathy in a mouse model. Using whole-exome sequencing, we identified three unrelated CNM-affected probands, including two with documented dilated cardiomyopathy, carrying homozygous or compound-heterozygous SPEG mutations. SPEG was markedly reduced or absent in two individuals whose muscle was available for immunofluorescence and immunoblot studies. Examination of muscle samples from Speg-knockout mice revealed an increased frequency of central nuclei, as seen in human subjects. SPEG localizes in a double line, flanking desmin over the Z lines, and is apparently in alignment with the terminal cisternae of the sarcoplasmic reticulum. Examination of human and murine MTM1-deficient muscles revealed similar abnormalities in staining patterns for both desmin and SPEG. Our results suggest that mutations in SPEG, encoding SPEG, cause a CNM phenotype as a result of its interaction with MTM1. SPEG is present in cardiac muscle, where it plays a critical role; therefore, individuals with SPEG mutations additionally present with dilated cardiomyopathy.

Acanthamoeba granulomatous amoebic encephalitis after pediatric hematopoietic stem cell transplant.

Acanthamoeba encephalitis is a rare, often fatal condition, particularly after HSCT, with 9 reported cases to date in the world literature. Our case was originally diagnosed with ALL at age 3 years, and after several relapses underwent HSCT at age 9 years. At 17 years of age, he was diagnosed with secondary AML for which he underwent a second allogeneic HSCT. He presented with acute-onset worsening neurological deficits on day +226 after the second transplant and a post-mortem diagnosis of Acanthamoeba encephalitis was established, with the aid of the CDC.

Cerebellopontine angle tumors in young children, displaying cranial nerve deficits, and restricted diffusion on diffusion-weighted imaging: a new clinical triad for atypical teratoid/rhabdoid tumors.

Atypical teratoid/rhabdoid tumors (AT/RT) of the central nervous system (CNS) are rare, highly malignant neoplasms that carry a poor prognosis. Even with prompt diagnosis, gross total resection and early initiation of intensive adjuvant therapy, the majority of patients will succumb within 9-12 months of diagnosis. The CPA location in children harbors lesions along a wide spectrum varying from benign to highly malignant. Imaging features of lesions within the CPA that aid the diagnostic process will help to initiate early treatment in higher-grade lesions. We report three cases, in very young children, all with cranial nerve deficits, who displayed CPA lesions with restricted diffusion on diffusion-weighted imaging (DWI) with pathology confirming AT/RT. We propose that in young children with a CPA tumor diffusion-weighted imaging should be routinely evaluated to aid in prompt management. In addition, the diagnosis of AT/RT should be highly suggestive in infants presenting with cranial nerve findings as well as DWI restricted diffusion within the CPA.

Characterization of MHC Class I and ß-2-Microglobulin Expression in Pediatric Solid Malignancies to Guide Selection of Immune-Based Therapeutic Trials.

BACKGROUND: Over 10,000 US children are diagnosed with cancer yearly. Though outcomes have improved by optimizing conventional therapies, recent immunotherapeutic successes in adult cancers are emerging. Cytotoxic T lymphocytes (CTLs) are the primary executioners of adaptive antitumor immunity and require antigenic presentation in the context of major histocompatibility complex (MHC) class I and the associated ß-2-microglobulin (B2M). Loss of MHC I expression is a common immune escape mechanism in adult malignancies, but pediatric cancers have not been thoroughly characterized. The essential nature of MHC I expression in CTL-mediated cell death may dictate the success of immunotherapies, which rely on eliciting an adaptive response. PROCEDURE: We queried pediatric tumor microarray databases for MHC I and B2M gene expression. We detected MHC I in pediatric tumor cell lines by flow cytometry and characterized MHC I and B2M expression in patient samples by immunohistochemistry. To determine whether therapeutic approaches might enhance MHC I expression in selected models in vitro, we tested effects of exposure to IFN-γ and histone deacetylase inhibitors. RESULTS: Pediatric tumors overall, as well as samples within select individual tumor subtypes, exhibit wide ranges of MHC I and B2M gene and protein expression. For most cell lines tested, MHC I was inducible in vitro. CONCLUSIONS: MHC I and B2M expression vary among pediatric tumor types and should be evaluated as potential biomarkers, which might identify patients most likely to benefit from MHC I dependent immunotherapies. Modulation of MHC I expression may be a promising mechanism for enhancing MHC I dependent immunotherapeutic efficacy.

SHH desmoplastic/nodular medulloblastoma and Gorlin syndrome in the setting of Down syndrome: case report, molecular profiling, and review of the literature.

INTRODUCTION: Individuals with Down syndrome (DS) have an increased risk of acute leukemia compared to a markedly decreased incidence of solid tumors. Medulloblastoma, the most common malignant brain tumor of childhood, is particularly rare in the DS population, with only one published case. As demonstrated in a mouse model, DS is associated with cerebellar hypoplasia and a decreased number of cerebellar granule neuron progenitor cells (CGNPs) in the external granule cell layer (EGL). Treatment of these mice with sonic hedgehog signaling pathway (Shh) agonists promote normalization of CGNPs and improved cognitive functioning. CASE REPORT: We describe a 21-month-old male with DS and concurrent desmoplastic/nodular medulloblastoma (DNMB)-a tumor derived from Shh dysregulation and over-activation of CGNPs. Molecular profiling further classified the tumor into the new consensus SHH molecular subgroup. Additional testing revealed a de novo heterozygous germ line mutation in the PTCH1 gene encoding a tumor suppressor protein in the Shh pathway. DISCUSSION: The developmental failure of CGNPs in DS patients offers a plausible explanation for the rarity of medulloblastoma in this population. Conversely, patients with PTCH1 germline mutations experience Shh overstimulation resulting in Gorlin (Nevoid Basal Cell Carcinoma) syndrome and an increased incidence of malignant transformation of CGNPs leading to medulloblastoma formation. This represents the first documented report of an individual with DS simultaneously carrying PTCH1 germline mutation. CONCLUSION: We have observed a highly unusual circumstance in which the PTCH1 mutation appears to "trump" the effects of DS in causation of Shh-activated medulloblastoma.

Enzyme replacement therapy rescues weakness and improves muscle pathology in mice with X-linked myotubular myopathy.

No effective treatment exists for patients with X-linked myotubular myopathy (XLMTM), a fatal congenital muscle disease caused by deficiency of the lipid phosphatase, myotubularin. The Mtm1δ4 and Mtm1 p.R69C mice model severely and moderately symptomatic XLMTM, respectively, due to differences in the degree of myotubularin deficiency. Contractile function of intact extensor digitorum longus (EDL) and soleus muscles from Mtm1δ4 mice, which produce no myotubularin, is markedly impaired. Contractile forces generated by chemically skinned single fiber preparations from Mtm1δ4 muscle were largely preserved, indicating that weakness was largely due to impaired excitation contraction coupling. Mtm1 p.R69C mice, which produce small amounts of myotubularin, showed impaired contractile function only in EDL muscles. Short-term replacement of myotubularin with a prototypical targeted protein replacement agent (3E10Fv-MTM1) in Mtm1δ4 mice improved contractile function and muscle pathology. These promising findings suggest that even low levels of myotubularin protein replacement can improve the muscle weakness and reverse the pathology that characterizes XLMTM.

Differential muscle hypertrophy is associated with satellite cell numbers and Akt pathway activation following activin type IIB receptor inhibition in Mtm1 p.R69C mice.

X-linked myotubular myopathy is a congenital myopathy caused by deficiency of myotubularin. Patients often present with severe perinatal weakness, requiring mechanical ventilation to prevent death from respiratory failure. We recently reported that an activin receptor type IIB inhibitor produced hypertrophy of type 2b myofibers and modest increases of strength and life span in the severely myopathic Mtm1δ4 mouse model of X-linked myotubular myopathy. We have now performed a similar study in the less severely symptomatic Mtm1 p.R69C mouse in hopes of finding greater treatment efficacy. Activin receptor type IIB inhibitor treatment of Mtm1 p.R69C animals produced behavioral and histological evidence of hypertrophy in gastrocnemius muscles but not in quadriceps or triceps. The ability of the muscles to respond to activin receptor type IIB inhibitor treatment correlated with treatment-induced increases in satellite cell number and several muscle-specific abnormalities of hypertrophic signaling. Treatment-responsive Mtm1 p.R69C gastrocnemius muscles displayed lower levels of phosphorylated ribosomal protein S6 and higher levels of phosphorylated eukaryotic elongation factor 2 kinase than were observed in Mtm1 p.R69C quadriceps muscle or in muscles from wild-type littermates. Hypertrophy in the Mtm1 p.R69C gastrocnemius muscle was associated with increased levels of phosphorylated ribosomal protein S6. Our findings indicate that muscle-, fiber type-, and mutation-specific factors affect the response to hypertrophic therapies that will be important to assess in future therapeutic trials.

A multi-resolution textural approach to diagnostic neuropathology reporting.

We present a computer aided diagnostic workflow focusing on two diagnostic branch points in neuropathology (intraoperative consultation and p53 status in tumor biopsy specimens) by means of texture analysis via discrete wavelet frames decomposition. For intraoperative consultation, our methodology is capable of classifying glioblastoma versus metastatic cancer by extracting textural features from the non-nuclei region of cytologic preparations based on the imaging characteristics of glial processes, which appear as anisotropic thin linear structures. For metastasis, these are homogeneous in appearance, thus suitable and extractable texture features distinguish the two tissue types. Experiments on 53 images (29 glioblastomas and 24 metastases) resulted in average accuracy as high as 89.7 % for glioblastoma, 87.5 % for metastasis and 88.7 % overall. For p53 interpretation, we detect and classify p53 status by classifying staining intensity into strong, moderate, weak and negative sub-classes. We achieved this by developing a novel adaptive thresholding for detection, a two-step rule based on weighted color and intensity for the classification of positively and negatively stained nuclei, followed by texture classification to classify the positively stained nuclei into the strong, moderate and weak intensity sub-classes. Our detection method is able to correctly locate and distinguish the four types of cells, at 85 % average precision and 88 % average sensitivity rate. These classification methods on the other hand recorded 81 % accuracy in classifying the positive and negative cells, and 60 % accuracy in further classifying the positive cells into the three intensity groups, which is comparable with neuropathologists' markings.

Modeling the human MTM1 p.R69C mutation in murine Mtm1 results in exon 4 skipping and a less severe myotubular myopathy phenotype.

X-linked myotubular myopathy (MTM) is a severe neuromuscular disease of infancy caused by mutations of MTM1, which encodes the phosphoinositide lipid phosphatase, myotubularin. The Mtm1 knockout (KO) mouse has a severe phenotype and its short lifespan (8 weeks) makes it a challenge to use as a model in the testing of certain preclinical therapeutics. Many MTM patients succumb early in life, but some have a more favorable prognosis. We used human genotype-phenotype correlation data to develop a myotubularin-deficient mouse model with a less severe phenotype than is seen in Mtm1 KO mice. We modeled the human c.205C>T point mutation in Mtm1 exon 4, which is predicted to introduce the p.R69C missense change in myotubularin. Hemizygous male Mtm1 p.R69C mice develop early muscle atrophy prior to the onset of weakness at 2 months. The median survival period is 66 weeks. Histopathology shows small myofibers with centrally placed nuclei. Myotubularin protein is undetectably low because the introduced c.205C>T base change induced exon 4 skipping in most mRNAs, leading to premature termination of myotubularin translation. Some full-length Mtm1 mRNA bearing the mutation is present, which provides enough myotubularin activity to account for the relatively mild phenotype, as Mtm1 KO and Mtm1 p.R69C mice have similar muscle phosphatidylinositol 3-phosphate levels. These data explain the basis for phenotypic variability among human patients with MTM1 p.R69C mutations and establish the Mtm1 p.R69C mouse as a valuable model for the disease, as its less severe phenotype will expand the scope of testable preclinical therapies.