Nuclear Factor I A and Nuclear Factor I B Are Jointly Required for Mouse Postnatal Neural Stem Cell Self-Renewal.

Mouse postnatal neural stem cells (pNSCs) can be expanded in vitro in the presence of epidermal growth factor and fibroblast growth factor 2 and upon removal of these factors cease proliferation and generate neurons, astrocytes, and oligodendrocytes. The genetic requirements for self-renewal and lineage-commitment of pNSCs are incompletely understood. In this study, we show that the transcription factors NFIA and NFIB, previously shown individually, to be essential for the normal commitment of pNSCs to the astrocytic lineage in vivo, are jointly required for normal self-renewal of pNSCs in vitro and in vivo. Using conditional knockout alleles of Nfia and Nfib, we show that the simultaneous loss of these two genes under self-renewal conditions in vitro reduces the expression of the proliferation markers PCNA and Ki67, eliminates clonogenicity of the cells, reduces the number of cells in S phase, and induces aberrant differentiation primarily into the neuroblast lineage. This phenotype requires the loss of both genes and is not seen upon loss of Nfia or Nfib alone, nor with combined loss of Nfia and Nfix or Nfib and Nfix. These data demonstrate a unique combined requirement for both Nfia and Nfib for pNSC self-renewal.

The first endovascular rat glioma model for pre-clinical evaluation of intra-arterial therapeutics.

BACKGROUND: Several translational animal models have been described assessing intra-arterial (IA) treatments for malignant gliomas. We describe the first endovascular animal model that allows testing of IA drug delivery as a first-line treatment, which is difficult to do in actual patients. We report a unique protocol for vascular access and IA delivery in the rat model that, unlike prior reports, does not require direct puncture and opening of proximal cerebrovasculature which carries risk of ischemia in the animal brain post-delivery. METHODS: Wistar rats underwent left femoral artery catherization with a Balt Magic 1.2F catheter or Marathon Flow directed 1.5F Microcatheter with an Asahi Chikai 0.008 micro-guidewire which was navigated to the left internal carotid artery under x-ray. 25% mannitol was administered to test blood brain barrier breakdown (BBBB). Additional rats were implanted with C6 glioma cells in the left frontal lobe. C6 Glioma-Implanted Rats (C6GRs) were monitored for overall survival and tumor growth. Tumor volumes from MRI images were calculated utilizing 3D slicer. Additional rats underwent femoral artery catheterization with Bevacizumab, carboplatin, or irinotecan injected into the left internal carotid artery to test feasibility and safety. RESULTS: A successful endovascular access and BBBB protocol was established. BBBB was confirmed with positive Evans blue staining. 10 rats were successfully implanted with C6 gliomas with confirmed growths on MRI. Overall survival was 19.75 ± 2.21 days. 5 rats were utilized for the development of our femoral catheterization protocol and BBBB testing. With regards to IA chemotherapy dosage testing, control rats tolerated targeted 10 mg/kg of bevascizumab, 2.4 mg/kg of carboplatin, and 15 mg/kg of irinotecan IA ICA injections without any complications. CONCLUSIONS: We present the first endovascular IA rat glioma model that allows selective catheterization of the intracranial vasculature and assessment of IA therapies for gliomas without need for access and sacrifice of proximal cerebrovasculature.

Defining the Intravital Renal Disposition of Fluorescence-Quenched Exenatide.

Despite the understanding that renal clearance is pivotal for driving the pharmacokinetics of numerous therapeutic proteins and peptides, the specific processes that occur following glomerular filtration remain poorly defined. For instance, sites of catabolism within the proximal tubule can occur at the brush border, within lysosomes following endocytosis, or even within the tubule lumen itself. The objective of the current study was to address these limitations and develop methodology to study the kidney disposition of a model therapeutic protein. Exenatide is a peptide used to treat type 2 diabetes mellitus. Glomerular filtration and ensuing renal catabolism have been shown to be its principal clearance pathway. Here, we designed and validated a Förster resonance energy transfer-quenched exenatide derivative to provide critical information on the renal handling of exenatide. A combination of in vitro techniques was used to confirm substantial fluorescence quenching of intact peptide that was released upon proteolytic cleavage. This evaluation was then followed by an assessment of the in vivo disposition of quenched exenatide directly within kidneys of living rats via intravital two-photon microscopy. Live imaging demonstrated rapid glomerular filtration and identified exenatide metabolism occurred within the subapical regions of the proximal tubule epithelia, with subsequent intracellular trafficking of cleaved fragments. These results provide a novel examination into the real-time, intravital disposition of a protein therapeutic within the kidney and offer a platform to build upon for future work.

Gene expression profiles of ischemic stroke clots retrieved by mechanical thrombectomy are associated with disease etiology.

BACKGROUND: Determining stroke etiology is crucial for secondary prevention, but intensive workups fail to classify ~30% of strokes that are cryptogenic. OBJECTIVE: To examine the hypothesis that the transcriptomic profiles of clots retrieved during mechanical thrombectomy are unique to strokes of different subtypes. METHODS: We isolated RNA from the clots of 73 patients undergoing mechanical thrombectomy. Samples of sufficient quality were subjected to 100-cycle, paired-end RNAseq, and transcriptomes with less than 10 million unique reads were excluded from analysis. Significant differentially expressed genes (DEGs) between subtypes (defined by the Trial of Org 10 172 in Acute Stroke Treatment) were identified by expression analysis in edgeR. Gene ontology enrichment analysis was used to study the biologic differences between stroke etiologies. RESULTS: In all, 38 clot transcriptomes were analyzed; 6 from large artery atherosclerosis (LAA), 21 from cardioembolism (CE), 5 from strokes of other determined origin, and 6 from cryptogenic strokes. Among all comparisons, there were 816 unique DEGs, 174 of which were shared by at least two comparisons, and 20 of which were shared by all three. Gene ontology analysis showed that CE clots reflected high levels of inflammation, LAA clots had greater oxidoreduction and T-cell processes, and clots of other determined origin were enriched for aberrant platelet and hemoglobin-related processes. Principal component analysis indicated separation between these subtypes and showed cryptogenic samples clustered among several different groups. CONCLUSIONS: Expression profiles of stroke clots were identified between stroke etiologies and reflected different biologic responses. Cryptogenic thrombi may be related to multiple etiologies.

Unconjugated p-cresol activates macrophage macropinocytosis leading to increased LDL uptake.

Patients with chronic kidney disease (CKD) and end-stage renal disease suffer from increased cardiovascular events and cardiac mortality. Prior studies have demonstrated that a portion of this enhanced risk can be attributed to the accumulation of microbiota-derived toxic metabolites, with most studies focusing on the sulfonated form of p-cresol (PCS). However, unconjugated p-cresol (uPC) itself was never assessed due to rapid and extensive first-pass metabolism that results in negligible serum concentrations of uPC. These reports thus failed to consider the host exposure to uPC prior to hepatic metabolism. In the current study, not only did we measure the effect of altering the intestinal microbiota on lipid accumulation in coronary arteries, but we also examined macrophage lipid uptake and handling pathways in response to uPC. We found that atherosclerosis-prone mice fed a high-fat diet exhibited significantly higher coronary artery lipid deposits upon receiving fecal material from CKD mice. Furthermore, treatment with uPC increased total cholesterol, triglycerides, and hepatic and aortic fatty deposits in non-CKD mice. Studies employing an in vitro macrophage model demonstrated that uPC exposure increased apoptosis whereas PCS did not. Additionally, uPC exhibited higher potency than PCS to stimulate LDL uptake and only uPC induced endocytosis- and pinocytosis-related genes. Pharmacological inhibition of varying cholesterol influx and efflux systems indicated that uPC increased macrophage LDL uptake by activating macropinocytosis. Overall, these findings indicate that uPC itself had a distinct effect on macrophage biology that might have contributed to increased cardiovascular risk in patients with CKD.

Immunoglobulin G Is a Novel Substrate for the Endocytic Protein Megalin.

Therapeutic immunoglobulin G (IgG) antibodies comprise the largest class of protein therapeutics. Several factors that influence their overall disposition have been well-characterized, including target-mediated mechanics and convective flow. What remains poorly defined is the potential for non-targeted entry into various tissues or cell types by means of uptake via cell surface receptors at those sites. Megalin and cubilin are large endocytic receptors whose cooperative function plays important physiological roles at the tissues in which they are expressed. One such example is the kidney, where loss of either results in significant declines in proximal tubule protein reabsorption. Due to their diverse ligand profile and broad tissue expression, megalin and cubilin represent potential candidates for receptor-mediated uptake of IgG into various epithelia. Therefore, the objective of the current work was to determine if IgG was a novel ligand of megalin and/or cubilin. Direct binding was measured for human IgG with both megalin and the cubilin/amnionless complex. Additional work focusing on the megalin-IgG interaction was then conducted to build upon these findings. Cell uptake studies using megalin ligands for competitive inhibition or proximal tubule cells stably transduced with megalin-targeted shRNA constructs supported a role for megalin in the endocytosis of human IgG. Furthermore, a pharmacokinetic study using transgenic mice with a kidney-specific mosaic knockout of megalin demonstrated increased urinary excretion of human IgG in megalin knockout mice when compared to wild-type controls. These findings indicate that megalin is capable of binding and internalizing IgG via a high affinity interaction.

Megalin-mediated albumin endocytosis in cultured murine mesangial cells.

Endocytosis by podocytes is gaining increased attention as a biologic means of removing large proteins such as serum albumin from the glomerular barrier. Some of this function has been attributed to the megalin/cubilin (Lrp2/Cubn) receptor complex and the albumin recycling protein FcRn (Fcgrt). However, whether other glomerular cells possess the potential to perform this same phenomenon or express these proteins remains uncharacterized. Mesangial cells are uniquely positioned in glomeruli and represent a cell type capable of performing several diverse functions. Here, the expression of megalin and FcRn in murine mesangial cells along with the megalin adaptor protein Dab-2 (Dab2) was shown for the first time. Cubilin mRNA expression was detected, but the absence of the cubilin partner amnionless (Amn) suggested that cubilin is minimally functional, if at all, in these cells. Mesangial cell endocytosis of albumin was characterized and shown to involve a receptor-mediated process. Albumin endocytosis was significantly impaired (p < 0.01) under inducible megalin knockdown conditions in stably transduced mesangial cells. The current work provides both the novel identification of megalin and FcRn in mesangial cells and the functional demonstration of megalin-mediated albumin endocytosis.

Fecal microbiota analysis of polycystic kidney disease patients according to renal function: A pilot study.

IMPACT STATEMENT: The heterogeneity of the renal disease, therapeutic interventions, and the original cause of the renal failure, all directly affect the microbiota. We delineate in this report the direct effect of decreased renal function on the bacterial composition following stringent criteria to eliminate the possibilities of other confounding factors and dissect the direct effects of the uremic milieu. We analyzed the microbiome following three different approaches to further evaluate the effects of mild, moderate and advanced renal insufficiency on the microbiome. We also present here a detailed functional analysis of the projected altered pathways secondary to changes in the microbiome composition.

Increased megalin expression in early type 2 diabetes: role of insulin-signaling pathways.

The megalin/cubilin complex is responsible for the majority of serum protein reclamation in the proximal tubules. The current study examined if decreases in their renal expression, along with the albumin recycling protein neonatal Fc receptor (FcRn) could account for proteinuria/albuminuria in the Zucker diabetic fatty rat model of type 2 diabetes. Immunoblots of renal cortex samples obtained at worsening disease stages demonstrated no loss in megalin, cubilin, or FcRn, even when proteinuria was measured. Additionally, early diabetic rats exhibited significantly increased renal megalin expression when compared with controls (adjusted P < 0.01). Based on these results, the ability of insulin to increase megalin was examined in a clonal subpopulation of the opossum kidney proximal tubule cell line. Insulin treatments (24 h, 100 nM) under high glucose conditions significantly increased megalin protein ( P < 0.0001), mRNA ( P < 0.0001), and albumin endocytosis. The effect on megalin expression was prevented with inhibitors against key effectors of insulin intracellular signaling, phosphatidylinositide 3-kinase and Akt. Studies using rapamycin to inhibit the mechanistic target of rapamycin complex 1 (mTORC1) resulted in a loss of insulin-induced megalin expression. However, subsequent evaluation demonstrated these effects were independent of initial mTORC1 suppression. The presented results provide insight into the expression of megalin, cubilin, and FcRn in type 2 diabetes, which may be impacted by elevated insulin and glucose. Furthermore, proximal tubule endocytic activity in early diabetics may be enhanced, a process that could have a significant role in proteinuria-induced renal damage.

Chronic kidney disease, uremic milieu, and its effects on gut bacterial microbiota dysbiosis.

Several lines of evidence suggest that gut bacterial microbiota is altered in patients with chronic kidney disease (CKD), though the mechanism of which this dysbiosis takes place is not well understood. Recent studies delineated changes in gut microbiota in both CKD patients and experimental animal models using microarray chips. We present 16S ribosomal RNA gene sequencing of both stool pellets and small bowel contents of C57BL/6J mice that underwent a remnant kidney model and establish that changes in microbiota take place in the early gastrointestinal tract. Increased intestinal urea concentration has been hypothesized as a leading contributor to dysbiotic changes in CKD. We show that urea transporters (UT)-A and UT-B mRNA are both expressed throughout the whole gastrointestinal tract. The noted increase in intestinal urea concentration appears to be independent of UTs' expression. Urea supplementation in drinking water resulted in alteration in bacterial gut microbiota that is quite different than that seen in CKD. This indicates that increased intestinal urea concentration might not fully explain the CKD- associated dysbiosis.

Advanced glycation end products dietary restriction effects on bacterial gut microbiota in peritoneal dialysis patients; a randomized open label controlled trial.

The modern Western diet is rich in advanced glycation end products (AGEs). We have previously shown an association between dietary AGEs and markers of inflammation and oxidative stress in a population of end stage renal disease (ESRD) patients undergoing peritoneal dialysis (PD). In the current pilot study we explored the effects of dietary AGEs on the gut bacterial microbiota composition in similar patients. AGEs play an important role in the development and progression of cardiovascular (CVD) disease. Plasma concentrations of different bacterial products have been shown to predict the risk of incident major adverse CVD events independently of traditional CVD risk factors, and experimental animal models indicates a possible role AGEs might have on the gut microbiota population. In this pilot randomized open label controlled trial, twenty PD patients habitually consuming a high AGE diet were recruited and randomized into either continuing the same diet (HAGE, n = 10) or a one-month dietary AGE restriction (LAGE, n = 10). Blood and stool samples were collected at baseline and after intervention. Variable regions V3-V4 of 16s rDNA were sequenced and taxa was identified on the phyla, genus, and species levels. Dietary AGE restriction resulted in a significant decrease in serum Nε-(carboxymethyl) lysine (CML) and methylglyoxal-derivatives (MG). At baseline, our total cohort exhibited a lower relative abundance of Bacteroides and Alistipes genus and a higher abundance of Prevotella genus when compared to the published data of healthy population. Dietary AGE restriction altered the bacterial gut microbiota with a significant reduction in Prevotella copri and Bifidobacterium animalis relative abundance and increased Alistipes indistinctus, Clostridium citroniae, Clostridium hathewayi, and Ruminococcus gauvreauii relative abundance. We show in this pilot study significant microbiota differences in peritoneal dialysis patients' population, as well as the effects of dietary AGEs on gut microbiota, which might play a role in the increased cardiovascular events in this population and warrants further studies.

Galectin-1 Reduces Neuroinflammation via Modulation of Nitric Oxide-Arginase Signaling in HIV-1 Transfected Microglia: a Gold Nanoparticle-Galectin-1 "Nanoplex" a Possible Neurotherapeutic?

Galectins are a family of ß-galactoside-binding lectins that are important modulators of homeostasis in the central nervous system (CNS). Galectin-1 is a pivotal regulator of microglia activation that alters the immune balance from neurodegeneration to neuroprotection and could have therapeutic relevance in HIV associated neurocognitive disorders (HAND). We have previously shown that galectin-1 treatment decreased oxidative stress in microglia and hypothesize that the mechanism underlying this phenomenon is the cross regulatory interactions between Nitric oxide (NO) and Arginase I activity in microglia. We induced microglial activation and examined the effect of galectin-1 on the expression of various M1/M2 microglial phenotypic markers. Since, TNF-α is associated with activation of microglial cells involved in pathogenesis of neurodegenerative diseases, we treated HIV transfected human microglial cell cultures (CHME-5/HIV) with TNF-α followed by treatment with galectin-1, to examine the galectin-1 mediated neuro-modulatory response. Our results show that treatment of CHME-5/HIV microglia with galectin-1 reduced TNF-α induced oxidative stress by ~40%, and also significantly reduced iNOS gene expression and NO production while correspondingly increasing arginase-1, cationic amino acid transporter (CAT-1) gene expression and arginase activity. Galectin-1 treatment results in shifting microglia polarization from M1 toward the beneficial M2 phenotype which may prevent neurodegeneration and promote neuroprotection. Thus, our data suggests that galectin-1 treatment reduces neuroinflammation in the CNS microenvironment via the modulation of the NO-arginase network in microglia and thus could play a neuroprotective role in HAND. Further, the therapeutic potential of galectin-1 could be enhanced by conjugation of galectin-1 onto gold nanoparticles (Au-NP), resulting in a nanogold-galectin-1 (Au-Gal-1) multivalent complex that will have more clinical translational efficacy than free galectin-1 by virtue of increasing the payload influx.

Central role for marginal zone B cells in an animal model of Sjogren's syndrome.

Patients with Sjogren's syndrome (SS) have been shown to have abnormal B cell function and increased numbers of marginal zone B cells (MZB and MZB precursors. The current studies utilized the Interleukin 14 alpha transgenic mouse model (IL14aTG) for SS to investigate the roles of marginal zone B cells (MZB) of the innate immune system in the pathophysiology of the disease. Eliminating MZB from IL14aTG mice by B cell specific deletion of RBP-J resulted in complete elimination of all disease manifestations of SS. Mice had normal salivary gland secretions, negative autoantibodies and normal histology of the salivary and lacrimal glands compared to IL14aTG mice at the same time points. In contrast, eliminating B1 cells by deleting btk did not ameliorate the disease. Therefore, MZB are critical for the development of SS.

Abrogation of immune complex glomerulonephritis by native carboxypeptidase and pharmacological antagonism of the C5a receptor.

Activation of complement generates C5a which leads to signaling through C5aR1. This is tightly controlled, including by the plasma proteins factor H (FH) and carboxypeptidase N. Here we studied a chronic serum sickness (CSS) model of glomerulonephritis (GN) in which there is an active humoral immune response, formation of glomerular immune complexes (ICs), and resulting glomerular inflammation. The antibody response, glomerular IC deposition, the degree of GN, and consequent renal functional insufficiency in CSS were all worse in FH-/- mice compared to wild-type FH+/+ animals. This was ameliorated in the former by giving a C5aR1 antagonist for the final 3 weeks of the 5-week protocol. In contrast, blocking CP-mediated inactivation of C5a increased these disease measures. Thus, complement regulation by both plasma FH and CP to limit the quantity of active C5a is important in conditions where the humoral immune response is directed to a continuously present foreign antigen. Signaling through C5aR1 enhances the humoral immune response as well as the inflammatory response to ICs that have formed in glomeruli. Both effects are relevant even after disease has begun. Thus, pharmacological targeting of C5a in IC-mediated GN has potential clinical relevance.

CD11b is protective in complement-mediated immune complex glomerulonephritis.

In chronic serum sickness, glomerular immune complexes form, yet C57BL/6 mice do not develop glomerulonephritis unless complement factor H (CfH) is absent, indicating the relevance of complement regulation. Complement receptor 3 (CD11b) and Fcγ receptors on leukocytes, and CfH on platelets, can bind immune complexes. Here we induced immune complex-mediated glomerulonephritis in CfH(-/-) mice chimeric for wild-type, CfH(-/-), CD11b(-/-), or FcRγ(-/-) bone marrow stem cells. Glomerulonephritis was worse in CD11b(-/-) chimeras compared with all others, whereas disease in FcRγ(-/-) and wild-type chimeras was comparable. Disease tracked strongly with humoral immune responses, but not glomerular immune complex deposits. Interstitial inflammation with M1 macrophages strongly correlated with glomerulonephritis scores. CD11b(-/-) chimeras had significantly more M1 macrophages and CD4(+) T cells. The renal dendritic cell populations originating from bone marrow-derived CD11c(+) cells were similar in all experimental groups. CD11b(+) cells bearing colony-stimulating factor 1 receptor were present in kidneys, including CD11b(-/-) chimeras; these cells correlated negatively with glomerulonephritis scores. Thus, experimental immune complex-mediated glomerulonephritis is associated with accumulation of M1 macrophages and CD4(+) T cells in kidneys and functional renal insufficiency. Hence, CD11b on mononuclear cells is instrumental in generating an anti-inflammatory response in the inflamed kidney.

Contrasting effects of systemic monocyte/macrophage and CD4+ T cell depletion in a reversible ureteral obstruction mouse model of chronic kidney disease.

Using a reversible UUO model (rUUO), we have demonstrated that C57BL/6 mice are susceptible to development of CKD after obstruction-mediated kidney injury while BALB/c mice are resistant. We hypothesized that selective systemic depletion of subpopulations of inflammatory cells during injury or repair might alter the development of CKD. To investigate the impact of modification of Th-lymphocytes or macrophage responses on development of CKD after rUUO, we used an anti-CD4 antibody (GK1.5) or liposomal clodronate to systemically deplete CD4(+) T cells or monocyte/macrophages, respectively, prior to and throughout the rUUO protocol. Flow cytometry and immunohistochemistry confirmed depletion of target cell populations. C57BL/6 mice treated with the GK1.5 antibody to deplete CD4(+) T cells had higher BUN levels and delayed recovery from rUUO. Treatment of C57BL/6 mice with liposomal clodronate to deplete monocyte/macrophages led to a relative protection from CKD as assessed by BUN values. Our results demonstrate that modulation of the inflammatory response during injury and repair altered the susceptibility of C57BL/6 mice to development of CKD in our rUUO model.

Defining the turkey MHC: identification of expressed class I- and class IIB-like genes independent of the MHC-B.

The MHC of the turkey (Meleagris gallopavo) is divided into two genetically unlinked regions; the MHC-B and MHC-Y. Although previous studies found the turkey MHC-B to be highly similar to that of the chicken, little is known of the gene content and extent of the MHC-Y. This study describes two partially overlapping large-insert BAC clones that genetically and physically map to the turkey MHC chromosome (MGA18) but to a region that assorts independently of MHC-B. Within the sequence assembly, 14 genes were predicted including new class I- and class IIB-like loci. Additional unassembled sequences corresponded to multiple copies of the ribosomal RNA repeat unit (18S-5.8S-28S). Thus, this newly identified MHC region appears to represent a physical boundary of the turkey MHC-Y. High-resolution multi-color fluorescence in situ hybridization studies confirm rearrangement of MGA18 relative to the orthologous chicken chromosome (GGA16) in regard to chromosome architecture, but not gene order. The difference in centromere position between the species is indicative of multiple chromosome rearrangements or alternate events such as neocentromere formation/centromere inactivation in the evolution of the MHC chromosome. Comparative sequencing of commercial turkeys (six amplicons totaling 7.6 kb) identified 68 single nucleotide variants defining nine MHC-Y haplotypes. Sequences of the new class I- and class IIB-like genes are most similar to MHC-Y genes in the chicken. All three loci are expressed in the spleen. Differential transcription of the MHC-Y class IIB-like loci was evident as one class IIB-like locus was only expressed in some individuals.

Haplotype variation, recombination, and gene conversion within the turkey MHC-B locus.

The major histocompatibility complex (MHC) is a gene dense region with profound effects on the disease phenotype. In many species, characterizations of MHC polymorphisms have focused on identifying allelic haplotypes of the highly polymorphic class I and class II loci through direct immunological approaches such as monoclonal antibodies specific for the major antigens or indirectly through DNA sequence-based approaches. Invariably, these studies fail to assess the broader range of variation at the other loci within the MHC. This study examines variation in the turkey MHC by resequencing 15 interspersed amplicons ( approximately 14 kb) spaced across the MHC-B locus in a representative sampling of 52 commercial birds. Over 200 single nucleotide polymorphisms (SNPs) were identified with high levels of polymorphism (1 SNP/70 bp) and heterozygosity (average minor allele frequency of 0.15). SNP genotypes were used to identify the major haplotypes segregating in the commercial lines. Sequencing of the peptide binding region (PBR, exon 2) of the class IIB loci of select individuals identified 10 PBR alleles/isotypes among the major MHC haplotypes. Examination of pedigreed families provides direct evidence of gene conversion and recombination within the B locus. Results of this study demonstrate the MHC diversity available in commercial flocks and provide genomic resources for studying the effect of this diversity (alleles and/or haplotypes) on disease susceptibility and resistance.

Defining the turkey MHC: sequence and genes of the B locus.

The MHC, the most polymorphic and gene dense region in the vertebrate genome, contains many loci essential to immunity. In mammals, this region spans approximately 4 Mb. Studies of avian species have found the MHC to be greatly reduced in size and gene content with an overall locus organization differing from that of mammals. The chicken MHC has been mapped to two distinct regions (MHC-B and -Y) of a single chromosome. MHC-B haplotypes possess tightly linked genes encoding the classical MHC molecules and few other disease resistance genes. Furthermore, chicken haplotypes possess a dominantly expressed class I and class II B locus that have a significant effect on the progression or regression of pathogenic disease. In this study, we present the MHC-B region of the turkey (Meleagris gallopavo) as a similarly constricted locus, with 34 genes identified within a 0.2-Mb region in near-perfect synteny with that of the chicken MHC-B. Notable differences between the two species are three BG and class II B loci in the turkey compared with one BG and two class II B loci in the chicken MHC-B. The relative size and high level of similarity of the turkey MHC in relation to that of the chicken suggest that similar associations with disease susceptibility and resistance may also be found in turkey.

Association and in silico assignment of sequences from turkey BACs.

Bacterial artificial chromosomes (BACs) provide an important resource in genetic mapping. An initial set of BACs corresponding to microsatellite markers in the turkey (Meleagris gallopavo) was isolated from the CHORI-260 turkey BAC library. The selected markers were distributed on both macro- and microchromosomes and included a genetically unlinked marker. End sequences were obtained for a subset of the recovered BACs and compared to the chicken whole genome sequence. Close association of the turkey BAC-end sequences and original marker sequences was generally conserved in the chicken genome. Gene content of the turkey BACs is predicted from the comparative sequence alignments.