Joseph A. Picoraro

Mutations in SLC1A4 , encoding the brain serine transporter, are associated with developmental delay, microcephaly and hypomyelination

Background L-serine plays an essential role in neuronal development and function. Although a non-essential amino acid, L-serine must be synthesised within the brain because of its poor permeability by the blood–brain barrier. Within the brain, its synthesis is confined to astrocytes, and its shuttle to neuronal cells is performed by a dedicated neutral amino acid transporter, ASCT1. Methods and results Using exome analysis we identified the recessive mutations, p.E256K, p.L315fs, and p.R457W, in SLC1A4, the gene encoding ASCT1, in patients with developmental delay, microcephaly and hypomyelination; seizure disorder was variably present. When expressed in a heterologous system, the mutations did not affect the protein level at the plasma membrane but abolished or markedly reduced L-serine transport for p.R457W and p.E256K mutations, respectively. Interestingly, p.E256K mutation displayed a lower L-serine and alanine affinity but the same substrate selectivity as wild-type ASCT1. Conclusions The clinical phenotype of ASCT1 deficiency is reminiscent of defects in L-serine biosynthesis. The data underscore that ASCT1 is essential in brain serine transport. The SLC1A4 p.E256K mutation has a carrier frequency of 0.7% in the Ashkenazi-Jewish population and should be added to the carrier screening panel in this community.

Identification and characterization of a novel DGAT1 missense mutation associated with congenital diarrhea

Acyl-CoA:diacylglycerol acyltransferase (DGAT)1 and DGAT2 catalyze triglyceride (TG) biosynthesis in humans. Biallelic loss-of-function mutations in human DGAT1 result in severe congenital diarrhea and protein-losing enteropathy. Additionally, pharmacologic inhibition of DGAT1 led to dose-related diarrhea in human clinical trials. Here we identify a previously unknown DGAT1 mutation in identical twins of South Asian descent. These male patients developed watery diarrhea shortly after birth, with protein-losing enteropathy and failure to thrive. Exome sequencing revealed a homozygous recessive mutation in DGAT1, c.314T>C, p.L105P. We show here that the p.L105P DGAT1 enzyme produced from the mutant allele is less abundant, resulting in partial loss of TG synthesis activity and decreased formation of lipid droplets in patient-derived primary dermal fibroblasts. Thus, in contrast with complete loss-of-function alleles of DGAT1, the p.L105P missense allele partially reduces TG synthesis activity and causes a less severe clinical phenotype. Our findings add to the growing recognition of DGAT1 deficiency as a cause of congenital diarrhea with protein-losing enteropathy and indicate that DGAT1 mutations result in a spectrum of diseases.

Phenotypic Heterogeneity of Neutropenia and Gastrointestinal Illness Associated with G6PC3 Founder Mutation.

Severe congenital neutropenia type IV (SCN IV) is a syndrome of severe neutropenia, cardiac and urogenital defects, prominent superficial veins, facial dysmorphism, failure to thrive (FTT), and intermittent thrombocytopenia, caused by a glucose-6-phosphatase catalytic subunit 3 (G6PC3) gene mutation. SCN IV has been linked to glycogen storage disease type 1b as both disorders involve disruption of the glucose-6-phosphatase/glucose-6-phosphate transporter complex, leading to arrested neutrophil maturation. Emerging evidence suggests that neutrophil function plays an important role in intestinal integrity, evidenced by inflammatory bowel disease in certain neutropenic patients. Here, we report 3 unrelated Hispanic males from the Dominican Republic with classic features of SCN IV found to share an identical inherited canonical splice-site mutation of the G6PC3 gene (c.218+1G>A). All 3 patients presented with severe FTT and gastrointestinal manifestations. Two of the patients had significant improvement in growth and resolution of gastrointestional symptoms with initiation of granulocyte colony-stimulating factor. We hypothesize that the gene variant described represents a founder mutation in the Dominican Republic, the first to be described in this geographical region. We discuss the potential associations between neutropenia and gastrointestinal disease with FTT and the role of granulocyte colony-stimulating factor in improving neutrophil count and intestinal integrity and growth.

Delineation of New Disorders and Phenotypic Expansion of Known Disorders Through Whole Exome Sequencing

Whole-exome sequencing (WES) has revolutionized gene discovery in human disease, drastically improving detection of pathogenic variation, expanding the delineation of molecular networks, enriching characterization of genomic architecture and refining the genotype–endophenotype distinctions in heterogeneous phenotypes. WES studies, often aided by collaborative consortia, have proven particularly effective in identifying the genetic etiology of autism, epilepsy, neurodevelopmental disabilities, brain malformations, congenital heart disease, congenital diaphragmatic hernia, multiple congenital anomalies, rare diseases, and the extreme phenotypes of common diseases. Analysis of proband and parents with a trio design has proven effective in the identification of de novo events and their contribution to disease, extending analysis of sporadic conditions beyond prior studies using comparative genomic hybridization and chromosome microarrays. WES has demonstrable utility in the clinical setting with impactful diagnostic yield across many diseases and is increasingly being adopted for its unbiased, efficient, and accurate ability to investigate the basis of human disease.

Pediatric Inflammatory Bowel Disease Clinical Innovations Meeting of the Crohn’s & Colitis Foundation: Charting the Future of Pediatric IBD

The Crohns & Colitis Foundation has facilitated transformational research in pediatric inflammatory bowel disease (IBD), through the RISK and PROTECT studies, that has laid the groundwork for a comprehensive understanding of molecular mechanisms of disease and predictors of therapeutic response in children. Despite these advances, children have lacked timely and informed access to the latest therapeutic advancements in IBD. The Crohns & Colitis Foundation convened a Pediatric Resource Organization for Kids with Inflammatory Intestinal Diseases (PRO-KIIDS) Clinical Innovations Meeting at the inaugural Crohns and Colitis Congress in January 2018 to devise how to advance the care of children with IBD. The working group selected 2 priorities: (1) accelerating therapies to children with IBD and (2) stimulating investigator-initiated research while fostering sustainable collaboration; and proposed 2 actions: (a) the convening of a task force to specifically address how to accelerate pharmacotherapies to children with IBD and (b) the funding of a multicenter clinical and translational research study that incorporates the building of critical research infrastructure.10.1093/ibd/izy205_video1izy205.video15799266615001.

Communicating the benefits and risks of inflammatory bowel disease therapy to patients and families

Purpose of review Treatment options for inflammatory bowel disease (IBD) have rapidly expanded as the treatment paradigm has shifted from controlling symptoms to reducing lifetime inflammatory burden. Families are confronted with the actual and perceived risks of this ever-expanding array of choices. We aim to review the shared decision-making process in pediatric IBD to ensure an optimal therapeutic plan for the child and their family. Recent findings Mucosal healing is a critical treatment target in pediatric IBD but it may not coincide with clinical symptoms. Evidence-based therapies carry important risks, some of which may be less severe than previously suspected, and a familys understanding of these risks plays a crucial role in how they make health decisions. To form an effective shared therapeutic plan, the physician must incorporate an understanding of the values of both the child and family along with their lived experience of illness. Summary To limit harm and promote health in pediatric IBD, the physician must communicate collaboratively with the child and their family to form mutually understood goals of care – both subjective experiential and objective biological – and appreciate actual and perceived risks of treatment options to effectively educate families and navigate toward the best treatment choices. Video abstract http://links.lww.com/MOP/A27

First Attempt of Sequential Living Donor Liver and Hematopoietic Stem Cell Transplantation in a Child With Advanced Hepatocellular Carcinoma: Case Report

Effective therapeutic options for advanced hepatocellular carcinoma are limited. Hematopoietic stem cell transplantation may offer a graft-versus-tumor effect. Combined liver and hematopoietic stem cell transplantation from the same donor with preparatory conditioning may promote tolerogenicity to the liver allograft and offers the potential for immunosuppression withdrawal. We report our experience with the use of this approach in a pediatric patient with invasive hepatocellular carcinoma and pulmonary metastases who underwent a living-donor liver transplantation followed by reduced-toxicity myeloablative conditioning and hematopoietic stem cell transplant from the same parental donor. Neutrophil engraftment and full donor chimerism was achieved without liver allograft dysfunction. Despite normal liver function and marrow engraftment, the patient succumbed to multisystem organ failure from disseminated toxoplasmosis. At autopsy, there was no histologic evidence of tumor recurrence. No pulmonary nodules were found. Regardless of the unfortunate overall result, this case demonstrates preliminary feasibility of sequential living-donor liver transplantation and hematopoietic stem cell transplantation for unresectable and metastasized hepatic tumors. Future studies in select pediatric patients require evaluation of the optimal conditioning regimen and prevention strategies for opportunistic infections to determine both graft-versus-tumor effect on hepatic tumors and durability of tolerogenicity and possible immunosuppression withdrawal.