Shayne Andrew

Partial MHC class II constructs inhibit MIF/CD74 binding and downstream effects.

MIF and its receptor, CD74, are pivotal regulators of the immune system. Here, we demonstrate for the first time that partial MHC class II constructs comprised of linked β1α1 domains with covalently attached antigenic peptides (also referred to as recombinant T‐cell receptor ligands — RTLs) can inhibit MIF activity by not only blocking the binding of rhMIF to immunopurified CD74, but also downregulating CD74 cell‐surface expression. This bifunctional inhibition of MIF/CD74 interactions blocked downstream MIF effects, including enhanced secretion of proinflammatory cytokines, anti‐apoptotic activity, and inhibition of random migration that all contribute to the reversal of clinical and histological signs of EAE. Moreover, we demonstrate that enhanced CD74 cell‐surface expression on monocytes in mice with EAE and subjects with multiple sclerosis can be downregulated by humanized RTLs, resulting in reduced MIF binding to the cells. Thus, binding of partial MHC complexes to CD74 blocks both the accessibility and availability of CD74 for MIF binding and downstream inflammatory activity.

Large-Scale Pooled Next-Generation Sequencing of 1077 Genes to Identify Genetic Causes of Short Stature

CONTEXT The majority of patients presenting with short stature do not receive a definitive diagnosis. Advances in genetic sequencing allow for large-scale screening of candidate genes, potentially leading to genetic diagnoses. OBJECTIVES The purpose of this study was to discover genetic variants that contribute to short stature in a cohort of children with no known genetic etiology. DESIGN This was a prospective cohort study of subjects with short stature. SETTING The setting was a pediatric endocrinology and genetics clinics at an academic center. PATIENTS A total of 192 children with short stature with no defined genetic etiology and 192 individuals of normal stature from the Framingham Heart Study were studied. INTERVENTION Pooled targeted sequencing using next-generation DNA sequencing technology of the exons of 1077 candidate genes was performed. MAIN OUTCOME MEASURES The numbers of rare nonsynonymous genetic variants found in case patients but not in control subjects, known pathogenic variants in case patients, and potentially pathogenic variants in IGF1R were determined. RESULTS We identified 4928 genetic variants in 1077 genes that were present in case patients but not in control subjects. Of those, 1349 variants were novel (898 nonsynonymous). False-positive rates from pooled sequencing were 4% to 5%, and the false-negative rate was 0.1% in regions covered well by sequencing. We identified 3 individuals with known pathogenic variants in PTPN11 causing undiagnosed Noonan syndrome. There were 9 rare potentially nonsynonymous variants in IGF1R, one of which is a novel, probably pathogenic, frameshift mutation. A previously reported pathogenic variant in IGF1R was present in a control subject. CONCLUSIONS Large-scale sequencing efforts have the potential to rapidly identify genetic etiologies of short stature, but data interpretation is complex. Noonan syndrome may be an underdiagnosed cause of short stature.

A novel regulatory pathway for autoimmune disease: Binding of partial MHC class II constructs to monocytes reduces CD74 expression and induces both specific and bystander T-cell tolerance

Treatment with partial (p)MHC class II-β1α1 constructs (also referred to as recombinant T-cell receptor ligands - RTL) linked to antigenic peptides can induce T-cell tolerance, inhibit recruitment of inflammatory cells and reverse autoimmune diseases. Here we demonstrate a novel regulatory pathway that involves RTL binding to CD11b(+) mononuclear cells through a receptor comprised of MHC class II invariant chain (CD74), cell-surface histones and MHC class II itself for treatment of experimental autoimmune encephalomyelitis (EAE). Binding of RTL constructs with CD74 involved a previously unrecognized MHC class II-α1/CD74 interaction that inhibited CD74 expression, blocked activity of its ligand, macrophage migration inhibitory factor, and reduced EAE severity. These findings implicate binding of RTL constructs to CD74 as a key step in both antigen-driven and bystander T-cell tolerance important in treatment of inflammatory diseases.

An XRCC4 splice mutation associated with severe short stature, gonadal failure, and early-onset metabolic syndrome

CONTEXT Severe short stature can be caused by defects in numerous biological processes including defects in IGF-1 signaling, centromere function, cell cycle control, and DNA damage repair. Many syndromic causes of short stature are associated with medical comorbidities including hypogonadism and microcephaly. OBJECTIVE To identify an underlying genetic etiology in two siblings with severe short stature and gonadal failure. DESIGN Clinical phenotyping, genetic analysis, complemented by in vitro functional studies of the candidate gene. SETTING An academic pediatric endocrinology clinic. PATIENTS OR OTHER PARTICIPANTS Two adult siblings (male patient [P1] and female patient 2 [P2]) presented with a history of severe postnatal growth failure (adult heights: P1, -6.8 SD score; P2, -4 SD score), microcephaly, primary gonadal failure, and early-onset metabolic syndrome in late adolescence. In addition, P2 developed a malignant gastrointestinal stromal tumor at age 28. INTERVENTION(S) Single nucleotide polymorphism microarray and exome sequencing. RESULTS Combined microarray analysis and whole exome sequencing of the two affected siblings and one unaffected sister identified a homozygous variant in XRCC4 as the probable candidate variant. Sanger sequencing and mRNA studies revealed a splice variant resulting in an in-frame deletion of 23 amino acids. Primary fibroblasts (P1) showed a DNA damage repair defect. CONCLUSIONS In this study we have identified a novel pathogenic variant in XRCC4, a gene that plays a critical role in non-homologous end-joining DNA repair. This finding expands the spectrum of DNA damage repair syndromes to include XRCC4 deficiency causing severe postnatal growth failure, microcephaly, gonadal failure, metabolic syndrome, and possibly tumor predisposition.

A Novel Variant in CDKN1C Is Associated With Intrauterine Growth Restriction, Short Stature, and Early-Adulthood-Onset Diabetes

CONTEXT CDKN1C, a cyclin-dependent kinase inhibitor and negative regulator of cellular proliferation, is paternally imprinted and has been shown to regulate β-cell proliferation. CDKN1C mutations are associated with growth disorders, including Beckwith-Wiedemann syndrome and IMAGe syndrome. OBJECTIVE To investigate the genetic basis for a familial disorder characterized by intrauterine growth restriction, short stature, and early-adulthood-onset diabetes. DESIGN, SETTING, AND PARTICIPANTS Genomic DNA samples (15 affected and 26 unaffected from a six-generation pedigree) were analyzed by genome-wide single nucleotide polymorphism arrays, whole exome and Sanger sequencing, and multiplex ligation-dependent probe amplification. MAIN OUTCOME MEASURE(S) Subjects were assessed for height, weight, adrenal gland size, ACTH, diabetes status, and testis volume. Linkage and sequence analyses were performed, and the identified genetic variant was functionally evaluated in reconstitution studies. RESULTS The pedigree followed a paternally imprinted pattern of inheritance, and genetic linkage analysis identified a single significant 2.6-megabase locus on chromosome 11p15, within the imprinting center region 2. Multiplex ligation-dependent probe amplification did not detect copy number variants or methylation abnormalities. Whole exome sequencing revealed a single novel variant in the proliferating cell nuclear antigen-binding region of CDKN1C (c.842G>T, p.R281I) that co-segregated with affected status and, unlike variants found in IMAGe, did not entirely abrogate proliferating cell nuclear antigen binding. Clinical assessments revealed that affected individuals had low testicular volume but normal adrenal function. CONCLUSIONS We report a novel CDKN1C mutation associated with features of IMAGe syndrome, but without adrenal insufficiency or metaphyseal dysplasia, and characterized by early-adulthood-onset diabetes. Our data expand the range of phenotypes observed with CDKN1C defects and suggest that CDKN1C mutations may represent a novel monogenic form of diabetes.

Neuroprotective Effects of Recombinant T-cell Receptor Ligand in Autoimmune Optic Neuritis in HLA-DR2 Mice

PURPOSE Optic neuritis (ON) is a condition involving primary inflammation, demyelination, and axonal injury in the optic nerve and leads to apoptotic retinal ganglion cell (RGC) death, which contributes to the persistence of visual loss. Currently, ON has no effective treatment. The goal was to determine the effectiveness of immunotherapy with recombinant T-cell receptor ligand (RTL) in preventing ON in humanized HLA-DR2 transgenic mice. METHODS Experimental autoimmune encephalomyelitis (EAE) was induced with myelin oligodendrocyte glycoprotein in humanized HLA-DR2 (DRβ1*1501) transgenic mice. Five consecutive doses of RTL342M were administrated at the onset of ON. The development of autoimmune ON was assessed by histopathology at different time points. The levels of myelin loss, axonal loss, and RGC damage were examined by immunofluorescence. RESULTS HLA-DR2 mice developed chronic ON 2 days before EAE characterized by progressive neurodegeneration in both organs. RTL342M significantly suppressed inflammation in the optic nerve and spinal cord and provided protection for at least 30 days. Examination of myelin loss showed a marked suppression of demyelination and an increase in myelin recovery in the optic nerve. Moreover, RTL342M treatment revealed a neuroprotective effect on optic nerve axons and RGCs in retinas at postimmunization (PI) day 62. CONCLUSIONS RTL342M suppressed clinical and histologic signs of EAE/ON by preventing the recruitment of inflammatory cells into the optic nerve and showed neuroprotective effects against ON. However, to achieve full therapeutic benefit, more doses may be needed. These findings suggest a possible clinical application of this novel class of T-cell-tolerizing drugs for patients with optic neuritis.

TCR-like antibodies distinguish conformational and functional differences in two- versus four-domain auto reactive MHC class II–peptide complexes

Antigen‐presenting cell‐associated four‐domain MHC class II (MHC‐II) molecules play a central role in activating autoreactive CD4+ T cells involved in multiple sclerosis (MS) and type 1 diabetes (T1D). In contrast, two‐domain MHC‐II structures with the same covalently attached self‐peptide (recombinant T‐cell receptor ligands (RTLs)) can regulate pathogenic CD4+ T cells and reverse clinical signs of experimental autoimmune diseases. RTL1000, which is composed of the β1α1 domains of human leukocyte antigen (HLA)‐DR2 linked to the encephalitogenic human myelin oligodendrocyte glycoprotein (MOG)‐35‐55 peptide, was recently shown to be safe and well tolerated in a phase I clinical trial in MS. To evaluate the opposing biological effects of four‐ versus two‐domain MHC‐II structures, we screened phage Fab antibodies (Abs) for the neutralizing activity of RTL1000. Five different TCR‐like Abs were identified that could distinguish between the two‐ versus four‐domain MHC–peptide complexes while the cognate TCR was unable to make such a distinction. Moreover, Fab detection of native two‐domain HLA‐DR structures in human plasma implies that there are naturally occurring regulatory MHC–peptide complexes. These results demonstrate for the first time distinct conformational determinants characteristic of activating versus tolerogenic MHC–peptide complexes involved in human autoimmunity.

A Novel GHR Intronic Variant, c.266+83G>T, Activates a Cryptic 5′ Splice Site Causing Severe GHR Deficiency and Classical GH Insensitivity Syndrome

Background/Aims: Mutations in the human growth hormone receptor gene (GHR) are the most common cause of growth hormone insensitivity (GHI) syndrome and insulin-like growth factor (IGF-1) deficiency. The extracellular domain of GHR (encoded by exons 2-7 of the GHR gene) can be proteolytically cleaved to circulate as GH-binding protein (GHBP). Methods: We evaluated the cause of classical GHI (Laron) phenotypes in 3 siblings. Results: Two brothers (aged 16.5 and 14.9 years) and their half-brother (aged 11.3 years) presented with extreme short stature (height standard deviation score, SDS, of -7.05, -6.34 and -8.02, respectively). The parents were consanguineous and of normal stature. Serum GHBP levels of probands were undetectable and circulating IGF-1 and IGF-binding protein-3 were abnormally low, but GH concentrations were elevated. Molecular analysis of the GHR gene revealed homozygous deletion of exon 3, a common polymorphism, and a novel c.266+83G>T variant within intron 4 which generated a 5′ donor splice site. Splicing events from this cryptic 5′ donor site resulted in retention of 81 intronic nucleotides in the GHR mRNA. Long-term rhIGF-1 therapy combined with leuprolide depot increased height by +2 to +3 SDS. Conclusion: The c.266+83G>T is the second intronic GHR mutation identified that activates a cryptic 5′ donor splice site. The abnormal splicing event led to early protein termination and undetectable serum GHBP concentrations.

Prevention and treatment of experimental autoimmune encephalomyelitis with clonotypic CDR3 peptides: CD4 + FoxP3 + T-regulatory cells suppress interleukin-2-dependent expansion of myelin basic protein-specific T cells

T‐cell receptor (TCR)‐derived peptides are recognized by the immune system and are capable of modulating autoimmune responses. Using the myelin basic protein (MBP) TCR 1501 transgenic mouse model, we demonstrated that TCR CDR3 peptides from the transgenic TCR can provide a protective effect when therapy is initiated before the induction of experimental autoimmune encephalomyelitis (EAE). More importantly, TCR CDR3 peptide therapy can ameliorate the disease when administered after EAE onset. Concurrent with the therapeutic effects, we observed reduced T‐cell proliferation and reduced interleukin‐2 (IL‐2) levels in response to stimulation with MBP‐85‐99 peptide in splenocyte cultures from mice receiving TCR CDR3 peptides compared with that of control mice. Moreover, we found that Foxp3+ CD4 T cells from mice protected with TCR CDR3 peptide are preferentially expanded in the presence of IL‐2. This is supportive of a proposed mechanism where Foxp3+ T‐regulatory cells induced by therapy with MBP‐85‐99 TCR CDR3 peptides limit expansion and the encephalitogenic activity of MBP‐85‐99‐specific T cells by regulating the levels of secreted IL‐2.

Expanding Genetic and Functional Diagnoses of IGF1R Haploinsufficiencies

Background: The growth-promoting effects of IGF-I is mediated through the IGF-I receptor (IGF1R), a widely expressed cell-surface tyrosine kinase receptor. IGF1R copy number variants (CNV) can cause pre- and postnatal growth restriction or overgrowth. Methods: Whole exome sequence (WES), chromosomal microarray, and targeted IGF1R gene analyses were performed on 3 unrelated children who share features of small for gestational age, short stature, and elevated serum IGF-I, but otherwise had clinical heterogeneity. Fluorescence-activated cell sorting (FACS) analysis of cell-surface IGF1R was performed on live primary cells derived from the patients. Results: Two novel IGF1R CNV and a heterozygous IGF1R nonsense variant were identified in the 3 patients. One CNV (4.492 Mb) was successfully called from WES, utilizing eXome-Hidden Markov Model (XHMM) analysis. FACS analysis of cell-surface IGF1R on live primary cells derived from the patients demonstrated a ∼50% reduction in IGF1R availability associated with the haploinsufficiency state. Conclusion: In addition to conventional methods, IGF1R CNV can be identified from WES data. FACS analysis of live primary cells is a promising method for efficiently evaluating and screening for IGF1R haploinsufficiency. Further investigations are necessary to delineate how comparable IGF1R availability leads to the wide spectrum of clinical phenotypes and variable responsiveness to rhGH therapy.