Increased expression of schizophrenia-associated gene C4 leads to hypoconnectivity of prefrontal cortex and reduced social interaction

Schizophrenia is a severe mental disorder with an unclear pathophysiology. Increased expression of the immune gene C4 has been linked to a greater risk of developing schizophrenia; however, it is not known whether C4 plays a causative role in this brain disorder. Using confocal imaging and whole-cell electrophysiology, we demonstrate that overexpression of C4 in mouse prefrontal cortex neurons leads to perturbations in dendritic spine development and hypoconnectivity, which mirror neuropathologies found in schizophrenia patients. We find evidence that microglia-mediated synaptic engulfment is enhanced with increased expression of C4. We also show that C4-dependent circuit dysfunction in the frontal cortex leads to decreased social interactions in juvenile and adult mice. These results demonstrate that increased expression of the schizophrenia-associated gene C4 causes aberrant circuit wiring in the developing prefrontal cortex and leads to deficits in juvenile and adult social behavior, suggesting that altered C4 expression contributes directly to schizophrenia pathogenesis.

Elevated expression of the gene encoding complement C4 is associated with an enhanced risk of schizophrenia, but the mechanism underlying this link is unclear. This study shows that overexpression of the C4 gene in mice leads to mis-wiring of the prefrontal cortex and deficits in social interactions.

Heterochromatin anomalies and double-stranded RNA accumulation underlie C9orf72 poly(PR) toxicity

How hexanucleotide GGGGCC (G4C2) repeat expansions in C9orf72 cause frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) is not understood. We developed a mouse model engineered to express poly(PR), a proline-arginine (PR) dipeptide repeat protein synthesized from expanded G4C2 repeats. The expression of green fluorescent protein-conjugated (PR)50 (a 50-repeat PR protein) throughout the mouse brain yielded progressive brain atrophy, neuron loss, loss of poly(PR)-positive cells, and gliosis, culminating in motor and memory impairments. We found that poly(PR) bound DNA, localized to heterochromatin, and caused heterochromatin protein 1α (HP1α) liquid-phase disruptions, decreases in HP1α expression, abnormal histone methylation, and nuclear lamina invaginations. These aberrations of histone methylation, lamins, and HP1α, which regulate heterochromatin structure and gene expression, were accompanied by repetitive element expression and double-stranded RNA accumulation. Thus, we uncovered mechanisms by which poly(PR) may contribute to the pathogenesis of C9orf72-associated FTD and ALS.

Poly(GP) proteins are a useful pharmacodynamic marker for C9ORF72-associated amyotrophic lateral sclerosis

There is no effective treatment for amyotrophic lateral sclerosis (ALS), a devastating motor neuron disease. However, discovery of a G₄C₂ repeat expansion in the C9ORF72 gene as the most common genetic cause of ALS has opened up new avenues for therapeutic intervention for this form of ALS. G₄C₂ repeat expansion RNAs and proteins of repeating dipeptides synthesized from these transcripts are believed to play a key role in C9ORF72-associated ALS (c9ALS). Therapeutics that target G₄C₂ RNA, such as antisense oligonucleotides (ASOs) and small molecules, are thus being actively investigated. A limitation in moving such treatments from bench to bedside is a lack of pharmacodynamic markers for use in clinical trials. We explored whether poly(GP) proteins translated from G₄C₂ RNA could serve such a purpose. Poly(GP) proteins were detected in cerebrospinal fluid (CSF) and in peripheral blood mononuclear cells from c9ALS patients and, notably, from asymptomatic C9ORF72 mutation carriers. Moreover, CSF poly(GP) proteins remained relatively constant over time, boding well for their use in gauging biochemical responses to potential treatments. Treating c9ALS patient cells or a mouse model of c9ALS with ASOs that target G₄C₂ RNA resulted in decreased intracellular and extracellular poly(GP) proteins. This decrease paralleled reductions in G₄C₂ RNA and downstream G₄C₂ RNA-mediated events. These findings indicate that tracking poly(GP) proteins in CSF could provide a means to assess target engagement of G₄C₂ RNA-based therapies in symptomatic C9ORF72 repeat expansion carriers and presymptomatic individuals who are expected to benefit from early therapeutic intervention.

A novel platform for engineering blood-brain barrier-crossing bispecific biologics

The blood-brain barrier (BBB) prevents the access of therapeutic antibodies to central nervous system (CNS) targets. The engineering of bispecific antibodies in which a therapeutic "arm" is combined with a BBB-transcytosing arm can significantly enhance their brain delivery. The BBB-permeable single-domain antibody FC5 was previously isolated by phenotypic panning of a naive llama single-domain antibody phage display library. In this study, FC5 was engineered as a mono- and bivalent fusion with the human Fc domain to optimize it as a modular brain delivery platform. In vitro studies demonstrated that the bivalent fusion of FC5 with Fc increased the rate of transcytosis (Papp) across brain endothelial monolayer by 25% compared with monovalent fusion. Up to a 30-fold enhanced apparent brain exposure (derived from serum and cerebrospinal fluid pharmacokinetic profiles) of FC5- compared with control domain antibody-Fc fusions after systemic dosing in rats was observed. Systemic pharmacological potency was evaluated in the Hargreaves model of inflammatory pain using the BBB-impermeable neuropeptides dalargin and neuropeptide Y chemically conjugated with FC5-Fc fusion proteins. Improved serum pharmacokinetics of Fc-fused FC5 contributed to a 60-fold increase in pharmacological potency compared with the single-domain version of FC5; bivalent and monovalent FC5 fusions with Fc exhibited similar systemic pharmacological potency. The study demonstrates that modular incorporation of FC5 as the BBB-carrier arm in bispecific antibodies or antibody-drug conjugates offers an avenue to develop pharmacologically active biotherapeutics for CNS indications.

An antibody-cytotoxic conjugate, BIIB015, is a new targeted therapy for Cripto positive tumours

BIIB015 is an immunoconjugate created for the treatment of solid tumours and is currently in Phase I of clinical evaluation. BIIB015 consists of a humanised monoclonal antibody against the Cripto protein carrying a payload, via a hindered disulphide linker, of the maytansinoid derivative, DM4. Cripto is a GPI-linked protein required for signal transduction of the TGF-beta ligand, Nodal. Cripto has been previously described as an oncogene and fits the classic pattern of an embryonic gene that is re-expressed in a transformed tumour cell. Cripto expression is highly prevalent on a number of solid tumours, including greater than 75% of breast, lung, and colorectal tumours. Our report documents for the first time that targeting the cell surface Cripto protein with an anti-Cripto antibody-cytotoxic conjugate is an effective means of inhibiting or regressing growth of Cripto positive tumours. BIIB015 which utilises a 'cleavable' linker containing a disulphide bond exhibits superior activity when compared to huB3F6 mAb conjugates with different linker systems, including one with a 'non-cleavable' linker. BIIB015 displays specificity for Cripto in both in vitro and in vivo experiments. In human xenograft models originating from lung (Calu-6), colon (CT-3), testicular (NCCIT) and breast (MDA-MB-231) tumour samples, BIIB015 shows robust activity with results ranging from >50% tumour inhibition to complete tumour regression. The efficacy seen in the MDA-MB-231 model, a triple negative (-HER2, -ER, and -PR) tumour, is particularly exciting since there is currently no approved therapy for this indication. In addition, BIIB015 can be combined with standard of care chemotherapeutics for enhanced efficacy.

Pathophysiologic role of alpha 4 integrins in the lung

Evidence for a central role for the integrins alpha 4 beta 1 and alpha 4 beta 7 in leukocyte pathophysiology is rapidly accumulating. Five distinct alpha 4 mAbs, each able to block alpha 4-dependent adhesion in vitro, show beneficial effects in vivo in six different species, and in a wide variety of organ systems, including colon, lung, skin, neural tissue, pancreas, peritoneum, and the vessel wall. In particular, a clear role for these integrins in lung pathophysiology is implied on the basis of in vivo studies in four different species. Although several issues remain to be resolved, including the relative importance of alpha 4 beta 1 and alpha 4 beta 7, and the relative roles of their counterligands, VCAM1, fibronectin, and MAdCAM, the data argue that alpha 4 integrins will likely be critical to both the normal physiology and pathology of the lung in man. To this end, we (Adams, Lin, Lobb, and Gill, unpublished data) and others have generated peptidomimetic small molecule antagonists of VLA4 based on the connecting segment 1 (CS1) peptide sequence of fibronectin that are potent blockers of integrin adhesive function in vitro and show efficacy in vivo. We have found that our inhibitors are excellent blockers of both murine contact hypersensitivity, and of the LPR and AHR in the sheep allergic airways model (Abraham, Lobb, Adams, and Gill, unpublished data), and are therefore possible candidates for clinical intervention in human asthma. The use of the VCAM-Ig fusion protein as a probe for high-affinity alpha 4 integrins has further enhanced our understanding of alpha 4 integrin function in the lung. While integrin upregulation in vitro has been observed many times, and high affinity (as opposed to avidity) of integrins seen in vitro in several systems, in vivo proof of integrin upregulation to a high-affinity state has been difficult to obtain in the absence of selective probes. Our data provide key information in this regard and strongly argue not only that integrin upregulation does indeed occur in vivo, but also that it is in fact obligatory for the leukocyte pathologies we have examined to date. Further studies are clearly warranted to further examine mechanisms of action, and to confirm and extend these studies, both with the alpha 4 integrins and with other integrin families. In summary, our studies of alpha 4 integrins continue to provide novel insights into the pathophysiology of integrin function and into future directions for drug discovery.

A direct binding assay for the vascular cell adhesion molecule-1 (VCAM1) interaction with alpha 4 integrins

Vascular cell adhesion molecule-1 (VCAM1) is a member of the immunoglobulin (Ig) superfamily which interacts with the alpha 4 integrins alpha 4 beta 1 (very late antigen 4: VLA4) and alpha 4 beta 7, which are constitutively expressed on many leukocyte subsets and play a key role in cell trafficking and activation. Using a recombinant VCAM-IgG fusion protein (VCAM-Ig) as a soluble ligand for alpha 4 beta 1 we directly demonstrated by fluorescence analysis that the alpha 4 beta 1 receptor can exist in different affinity states on the cell surface, and that a high affinity state is induced by manganese ions or certain activating anti-beta 1 monoclonal antibodies (Jakubowski et al., 1995b). Here we have extended these observations by developing a rapid and reproducible assay using alkaline phosphatase (AP)-coupled VCAM-Ig (VCAM-Ig-AP) which measures the interaction between VCAM1 and alpha 4 integrins in a microtiter plate format. This assay has allowed us to evaluate directly the effects of metal ions, anti-beta 1 mAbs, and different cell types and species on the VCAM1/alpha 4 integrin interaction. Most importantly, the assay system provides a means to rapidly evaluate alpha 4 integrin-directed inhibitors without the complication of post-ligand binding events inherent in adhesion assays.

GD3-reactive antibodies can inhibit the lysis of autologous tumor cells by tumor-infiltrating lymphocytes

GD3 is expressed in high concentrations on melanoma cells and may serve as a useful target antigen for mAb-mediated immunotherapy. Monoclonal antibodies (mAbs) against GD3 stimulate cell-mediated immune responses against tumor cells in vitro and this activity may contribute to antitumor effects in patients with melanoma treated with GD3-reactive mAbs. In the present study the effects of GD3-reactive mAbs on autologous tumor cell lysis by a human melanoma-derived tumor-infiltrating lymphocyte (TIL) population were examined. Unlike results reported for other GD3+ T cells isolated from melanoma patients, the tumor-specific lytic activity of the TIL line was inhibited by incubation with mAbs against GD3. Other melanoma-reactive mAbs, including those against GD2 and the high-molecular-weight melanoma-associated Ag, had no effect on the TIL lytic activity. Overall, these results indicate that mAbs against GD3 may have different effects on T cell/tumor cell interactions.

Increased tumor-specific CTL activity in human tumor-infiltrating lymphocytes stimulated with autologous tumor lines

Two long-term tumor-infiltrating lymphocyte (TIL) lines and their autologous tumor lines have been established from solid tumors derived from different patients with metastatic melanoma. In 4-hr 51Cr release assays, each TIL culture lysed only the autologous cryopreserved fresh or established melanoma line, but failed to lyse other melanoma tumors or K562 cells. Repeated stimulation of TIL with the autologous melanoma lines resulted in significant increases in anti-tumor CTL activity with no apparent loss in specificity. Stimulated cells have retained cytotoxic activity for up to 5 months in culture. Tumor cell CTL activity for both long-term TIL lines is inhibited by several mAbs, including those against CD3, CD8, and class I MHC molecules, indicating that the effector cells are class I-restricted CD8+, CTL. Furthermore, recognition of Ag on one of the established melanoma lines by TIL is restricted by HLA A-2. The availability of autologous tumor lines may prove clinically useful for the selective stimulation and expansion of cells with anti-tumor activity within a heterogeneous TIL population.

The use of microcapsules for high density growth of human tumor infiltrating lymphocytes and other immune reactive T cells

The use of microcapsules to achieve high density growth of tumor infiltrating lymphocytes (TIL) and other antigen-specific human T cells is described. Whereas human T cells in suspension cultures usually do not exceed 1-2 x 10(6) cells/ml, densities approaching that found in living tissues (greater than 10(8) cells/ml) have been observed for microcapsule cultures. TIL and human peripheral blood-derived T cells can be routinely recovered from microcapsules with viabilities greater than or equal to 90%. The recovered cells retain their antigen reactivities and bear cell surface phenotypes identical to their counterparts grown in suspension culture. These findings suggest that microcapsule technology could prove valuable in generating the vast numbers of cells required for TIL therapy and other forms of adoptive immunotherapy with T cells.

Analysis of hemoglobin F production in Saudi Arabian families with sickle cell anemia

Erythrocytes and progenitor-derived erythroblasts of sickle cell anemia patients from the Eastern Province of Saudi Arabia contain increased fetal hemoglobin and G gamma globin. A distinctive DNA polymorphism haplotype in the beta globin gene cluster (++- +-), tightly coupled to a C----T substitution at position -158 5' to the cap site of the G gamma globin gene, is strongly associated with sickle cell disease in this region. To determine whether the increased fetal hemoglobin production and/or elevated G gamma globin content are tightly linked to this haplotype, we studied 55 members of five Saudi families in which sickle cell disease is present. The results did not suggest a tight linkage of the haplotype to increased fetal hemoglobin production. On the other hand, several sickle trait family members heterozygous for the haplotype had normal fetal hemoglobin production in culture but elevated G gamma to A gamma ratios in peripheral blood. This observation suggests that in this genetic background increased expression of the G gamma globin gene may occur without a measurable increase in total fetal hemoglobin production. The family studies also clearly demonstrate that increased fetal hemoglobin production by erythroid progenitors is dependent on zygosity for the sickle gene in this population. These findings strongly suggest that other factors, such as the products of genes stimulated by hemolytic stress or other genetic determinants associated with the Saudi beta S chromosome, may interact with the -158 C----T substitution and influence gamma globin gene expression in this population.

Gamma-interferon alters globin gene expression in neonatal and adult erythroid cells

Interferons have the ability to enhance or diminish the expression of specific genes and have been shown to affect the proliferation of certain cells. Here, the effect of gamma-interferon on fetal hemoglobin synthesis by purified cord blood, fetal liver, and adult bone marrow erythroid progenitors was studied with a radioligand assay to measure hemoglobin production by BFU-E-derived erythroblasts. Coculture with recombinant gamma-interferon resulted in a significant and dose-dependent decrease in fetal hemoglobin production by neonatal and adult, but not fetal, BFU-E-derived erythroblasts. Accumulation of fetal hemoglobin by cord blood BFU-E-derived erythroblasts decreased up to 38.1% of control cultures (erythropoietin only). Synthesis of both G gamma/A gamma globin was decreased, since the G gamma/A gamma ratio was unchanged. Picograms fetal hemoglobin per cell was decreased by gamma-interferon addition, but picograms total hemoglobin was unchanged, demonstrating that a reciprocal increase in beta-globin production occurred in cultures treated with gamma-interferon. No toxic effect of gamma-interferon on colony growth was noted. The addition of gamma-interferon to cultures resulted in a decrease in the percentage of HbF produced by adult BFU-E-derived cells to 45.6% of control. Fetal hemoglobin production by cord blood, fetal liver, and adult bone marrow erythroid progenitors, was not significantly affected by the addition of recombinant GM-CSF, recombinant interleukin 1 (IL-1), recombinant IL-2, or recombinant alpha-interferon. Although fetal progenitor cells appear unable to alter their fetal hemoglobin program in response to any of the growth factors added here, the interaction of neonatal and adult erythroid progenitors with gamma-interferon results in an altered expression of globin genes. This supports the concept that developmental globin gene switching can be regulated by environmental factors.

Molecular analysis of the high-hemoglobin-F phenotype in Saudi Arabian sickle cell anemia

Patients from the eastern province of Saudi Arabia who have sickle cell anemia have high circulating levels of fetal hemoglobin (hemoglobin F, 17 percent), and they therefore have a mild form of the disease. To examine the molecular basis of the elevated production of hemoglobin F, we searched for mutations in the promoter regions of the two hemoglobin F gamma-globin genes (G gamma and A gamma). The DNA sequences 450 bp (base pairs) upstream of both the G gamma and A gamma globin genes were normal except for a single-base cytosine-to-thymidine (C----T) substitution at -158 bp 5' to the cap (preinitiation) site of the G gamma-globin gene of the high-hemoglobin-F chromosome. We searched for an association between this -158 C----T substitution and the production of hemoglobin F and G gamma in normal Saudis and Saudis with sickle cell disease or trait. The substitution was present in nearly 100 percent of the patients with sickle cell disease or trait, and in 22 percent of the normal Saudis. Homozygosity for this mutation had no demonstrable effect on hemoglobin F production in the normal Saudi population. We conclude that this mutation is not uniquely responsible for the increase in hemoglobin F in Saudi patients. It may nevertheless have an important role in regulating hemoglobin F production, but its expression is complex and requires interaction with additional factors, such as hemolytic stress or other molecular determinants, possibly linked to the sickle cell gene.

High fetal hemoglobin production in sickle cell anemia in the eastern province of Saudi Arabia is genetically determined

Homozygous sickle cell disease in the eastern province of Saudi Arabia is clinically mild. Circulating fetal hemoglobin levels of 16.0 +/- 7.4% were found in these anemic patients, but only 1.09 +/- 0.97% in their sickle trait parents. To determine whether these sickle cell anemia patients inherit an increased capacity to synthesize fetal hemoglobin, a radioimmunoassay of fetal and adult hemoglobin was performed on erythroid progenitor (BFU-E)-derived erythroblasts from Saudi Arabian sickle cell patients and their parents. Mean fetal hemoglobin content per BFU-E-derived erythroblast from Saudi Arabian sickle cell patients was 6.2 +/- 2.4 pg/cell or 30.4 +/- 8.6% fetal hemoglobin (normal 1.1 +/- 0.7 pg/cell and 5.1 +/- 1.8%). Linear regression analysis of % HbF in peripheral blood versus % HbF per BFU-E-derived cell showed a positive correlation with an r of 0.65. The variance of the intrinsic capacity to produce HbF may account for almost 40% (r2) of the variance of circulating fetal hemoglobin but other factors, particularly selective survival of F cells, must also contribute significantly. Despite virtually normal HbF levels in sickle trait parents of these Saudi patients, mean fetal hemoglobin production per BFU-E-derived erythroblast in these individuals was elevated to 3.42 +/- 1.79 pg/cell or 16.1 +/- 6.4% fetal hemoglobin, and the magnitude of fetal hemoglobin production found in parents correlated with that of the patients. These data indicate that the high fetal hemoglobin in Saudi sickle cell disease is genetically determined but expressed only during accelerated erythropoiesis. Further evidence of such genetic determination was provided by analysis of DNA polymorphisms within the beta-globin gene cluster on chromosome 11. This revealed a distinctive 5' globin haplotype (+ + - + +) on at least one chromosome 11 in all high F SS and AS tested. The precise relationship of this haplotype to HbF production in this population remains to be defined.

Identification of cell surface antigens present on murine hematopoietic stem cells

Nine antigens found on murine bone marrow cells were examined to define their pattern of expression in murine hematopoietic differentiation. Lymphocyte function antigen (LFA-1), heat stable antigen (recognized by M1/69), common leukocyte antigen (CLA, T200, Ly-5) and Lgp100a (recognized by 30-C7) were present on early hematopoietic progenitors, BFU-E, CFU-E, CFU-GM, and CFU-M. All antigens found on progenitors were found on some immature precursor cells, myeloblasts, erythroblasts, or monoblasts, but their pattern of expression on identifiable hematopoietic cells varied. Three of these antigens, LFA-1, heat stable antigen recognized by M1/69, and CLA, were expressed on leukocytes of all stages of maturity but were lost from the erythroid lineage during differentiation. MAC-1, Forssman antigen, heat stable antigen (recognized by M1/75), anti-P-95 (recognized by M5/113), and Ia (recognized by M5/114) were found only on differentiated hematopoietic precursors or mature cells. The expression of these antigens was more lineage-specific. MAC-1 and heat stable antigen (recognized by M1/75) were restricted to either mature myeloid or erythroid cells, respectively. The marked differences in distribution of these antigens suggest that they may be useful in negative or positive selection experiments to enrich progenitors, and that some of them may have a functional role in differentiation.

Identification of cell surface antigens present on murine hematopoietic stem cells

Nine antigens found on murine bone marrow cells were examined to define their pattern of expression in murine hematopoietic differentiation. Lymphocyte function antigen (LFA-1), heat stable antigen (recognized by M1/69), common leukocyte antigen (CLA, T200, Ly-5) and Lgp100a (recognized by 30-C7) were present on early hematopoietic progenitors, BFU-E, CFU-E, CFU-GM, and CFU-M. All antigens found on progenitors were found on some immature precursor cells, myeloblasts, erythroblasts, or monoblasts, but their pattern of expression on identifiable hematopoietic cells varied. Three of these antigens, LFA-1, heat stable antigen recognized by M1/69, and CLA, were expressed on leukocytes of all stages of maturity but were lost from the erythroid lineage during differentiation. MAC-1, Forssman antigen, heat stable antigen (recognized by M1/75), anti-P-95 (recognized by M5/113), and Ia (recognized by M5/114) were found only on differentiated hematopoietic precursors or mature cells. The expression of these antigens was more lineage-specific. MAC-1 and heat stable antigen (recognized by M1/75) were restricted to either mature myeloid or erythroid cells, respectively. The marked differences in distribution of these antigens suggest that they may be useful in negative or positive selection experiments to enrich progenitors, and that some of them may have a functional role in differentiation.