Enhancing CDK4/6 inhibitor therapy for medulloblastoma using nanoparticle delivery and scRNA-seq-guided combination with sapanisertib

The therapeutic potential of CDK4/6 inhibitors for brain tumors has been limited by recurrence. To address recurrence, we tested a nanoparticle formulation of CDK4/6 inhibitor palbociclib (POx-Palbo) in mice genetically-engineered to develop SHH-driven medulloblastoma, alone or in combination with specific agents suggested by our analysis. Nanoparticle encapsulation reduced palbociclib toxicity, enabled parenteral administration, improved CNS pharmacokinetics, and extended mouse survival, but recurrence persisted. scRNA-seq identified up-regulation of glutamate transporter Slc1a2 and down-regulation of diverse ribosomal genes in proliferating medulloblastoma cells in POx-Palbo-treated mice, suggesting mTORC1 signaling suppression, subsequently confirmed by decreased 4EBP1 phosphorylation. Combining POx-Palbo with the mTORC1 inhibitor sapanisertib produced mutually enhancing effects and prolonged mouse survival compared to either agent alone, contrasting markedly with other tested drug combinations. Our data show the potential of nanoparticle formulation and scRNA-seq analysis of resistance to improve brain tumor treatment and identify POx-Palbo + Sapanisertib as effective combinatorial therapy for SHH medulloblastoma.

Development of outbred CD1 mouse colonies with distinct standardized gut microbiota profiles for use in complex microbiota targeted studies

Studies indicate that the gut microbiota (GM) can significantly influence both local and systemic host physiologic processes. With rising concern for optimization of experimental reproducibility and translatability, it is essential to consider the GM in study design. However, GM profiles can vary between rodent producers making consistency between models challenging. To circumvent this, we developed outbred CD1 mouse colonies with stable, complex GM profiles that can be used as donors for a variety of GM transfer techniques including rederivation, co-housing, cross-foster, and fecal microbiota transfer (FMT). CD1 embryos were surgically transferred into CD1 or C57BL/6 surrogate dams that varied by GM composition and complexity to establish four separate mouse colonies harboring GM profiles representative of contemporary mouse producers. Using targeted 16S rRNA amplicon sequencing, subsequent female offspring were found to have similar GM profiles to surrogate dams. Furthermore, breeding colonies of CD1 mice with distinct GM profiles were maintained for nine generations, demonstrating GM stability within these colonies. To confirm GM stability, we shipped cohorts of these four colonies to collaborating institutions and found no significant variation in GM composition. These mice are an invaluable experimental resource that can be used to investigate GM effects on mouse model phenotype.

The Collaborative Cross as a resource for modeling human disease: CC011/Unc, a new mouse model for spontaneous colitis

Inflammatory bowel disease (IBD) is an immune-mediated condition driven by improper responses to intestinal microflora in the context of environmental and genetic background. GWAS in humans have identified many loci associated with IBD, but animal models are valuable for dissecting the underlying molecular mechanisms, characterizing environmental and genetic contributions and developing treatments. Mouse models rely on interventions such as chemical treatment or introduction of an infectious agent to induce disease. Here, we describe a new model for IBD in which the disease develops spontaneously in 20-week-old mice in the absence of known murine pathogens. The model is part of the Collaborative Cross and came to our attention due to a high incidence of rectal prolapse in an incompletely inbred line. Necropsies revealed a profound proliferative colitis with variable degrees of ulceration and vasculitis, splenomegaly and enlarged mesenteric lymph nodes with no discernible anomalies of other organ systems. Phenotypic characterization of the CC011/Unc mice with homozygosity ranging from 94.1 to 99.8% suggested that the trait was fixed and acted recessively in crosses to the colitis-resistant C57BL/6J inbred strain. Using a QTL approach, we identified four loci, Ccc1, Ccc2, Ccc3 and Ccc4 on chromosomes 12, 14, 1 and 8 that collectively explain 27.7% of the phenotypic variation. Surprisingly, we also found that minute levels of residual heterozygosity in CC011/Unc have significant impact on the phenotype. This work demonstrates the utility of the CC as a source of models of human disease that arises through new combinations of alleles at susceptibility loci.

Metastatic uterine adenocarcinoma in an 8-year-old gilt

An 8-y-old gilt was evaluated after the onset of hemorrhagic perineal discharge. Uterine adenocarcinoma with metastases to the lungs and regional lymph nodes was diagnosed at necropsy. Tumor cells lacked expression of estrogen receptor alpha and progesterone receptor. This case represents the first reported uterine adenocarcinoma in a research pig and the first swine uterine neoplasia in which steroid hormone receptor expression was evaluated.

Overexpression of Eg5 causes genomic instability and tumor formation in mice

Proper chromosome segregation in eukaryotes is driven by a complex superstructure called the mitotic spindle. Assembly, maintenance, and function of the spindle depend on centrosome migration, organization of microtubule arrays, and force generation by microtubule motors. Spindle pole migration and elongation are controlled by the unique balance of forces generated by antagonistic molecular motors that act upon microtubules of the mitotic spindle. Defects in components of this complex structure have been shown to lead to chromosome missegregation and genomic instability. Here, we show that overexpression of Eg5, a member of the Bim-C class of kinesin-related proteins, leads to disruption of normal spindle development, as we observe both monopolar and multipolar spindles in Eg5 transgenic mice. Our findings show that perturbation of the mitotic spindle leads to chromosomal missegregation and the accumulation of tetraploid cells. Aging of these mice revealed a higher incidence of tumor formation with a mixed array of tumor types appearing in mice ages 3 to 30 months with the mean age of 20 months. Analysis of the tumors revealed widespread aneuploidy and genetic instability, both hallmarks of nearly all solid tumors. Together with previous findings, our results indicate that Eg5 overexpression disrupts the unique balance of forces associated with normal spindle assembly and function, and thereby leads to the development of spindle defects, genetic instability, and tumors.

Targeted inactivation of Mdm2 RING finger E3 ubiquitin ligase activity in the mouse reveals mechanistic insights into p53 regulation

It is believed that Mdm2 suppresses p53 in two ways: transcriptional inhibition by direct binding, and degradation via its E3 ligase activity. To study these functions physiologically, we generated mice bearing a single-residue substitution (C462A) abolishing the E3 function without affecting p53 binding. Unexpectedly, homozygous mutant mice died before E7.5, and deletion of p53 rescued the lethality. Furthermore, reintroducing a switchable p53 by crossing with p53ER(TAM) mice surprisingly demonstrated that the mutant Mdm2(C462A) was rapidly degraded in a manner indistinguishable from that of the wild-type Mdm2. Hence, our data indicate that (1) the Mdm2-p53 physical interaction, without Mdm2-mediated p53 ubiquitination, cannot control p53 activity sufficiently to allow early mouse embryonic development, and (2) Mdm2's E3 function is not required for Mdm2 degradation.

Foxp3 controls autoreactive T cell activation through transcriptional regulation of early growth response genes and E3 ubiquitin ligase genes, independently of thymic selection

To elucidate the mechanisms of autoreactive T cell activation and expansion, we used endogenous viral superantigens (VSAg)-reactive T cells as a model of self-antigens in two strains of Foxp3-mutant mice. These two strains, together with wild-type mice, provided us with an advantage to simultaneously study the positively and negatively selected as well as rescued autoreactive T cells. We show here that while both VSAg-reactive and non-VSAg-reactive T cells are equally activated in Foxp3-mutant mice, only the VSAg-reactive T cells are preferentially expanded independently of their selected states in the thymus. The T cell activation appears to be controlled by Foxp3 through transcriptional regulation of early growth response (Egr) genes Egr-2 and Egr-3, and E3 ubiquitin (Ub) ligase genes Cblb, Itch and GRAIL, subsequently affecting degradation of two key signaling proteins, PLCgamma1 and PKC-theta. Physiologically, the positively, but not negatively selected VSAg-reactive T cells are spontaneously activated without significant expansion. The results suggest that autoreactive T cell activation is controlled by Foxp3 through transcriptional regulation of early growth response genes and E3 ubiquitin ligase genes, independently of thymic selection.

The Scurfy mutation of FoxP3 in the thymus stroma leads to defective thymopoiesis

The Scurfy mutation of the FoxP3 gene (FoxP3^sf) in the mouse and analogous mutations in human result in lethal autoimmunity. The mutation of FoxP3 in the hematopoietic cells impairs the development of regulatory T cells. In addition, development of the Scurfy disease also may require mutation of the gene in nonhematopoietic cells. The T cell–extrinsic function of FoxP3 has not been characterized. Here we show that the FoxP3^sf mutation leads to defective thymopoiesis, which is caused by inactivation of FoxP3 in the thymic stromal cells. FoxP3 mutation also results in overexpression of ErbB2 in the thymic stroma, which may be involved in defective thymopoiesis. Our data reveal a novel T cell–extrinsic function of FoxP3. In combination, the T cell–intrinsic and –extrinsic defects provide plausible explanation for the severity of the autoimmune diseases in the scurfy mice and in patients who have immunodysregulation, polyendocrinopathy, enteropathy, and X-linked syndrome.

Azoxymethane is a genetic background-dependent colorectal tumor initiator and promoter in mice: effects of dose, route, and diet

The azoxymethane (AOM) model has been widely used to investigate the pathology and genetics of colorectal cancer in rodents. However, there has been wide variation in treatment regimes, making it difficult to compare across studies. Consequently, standardizing AOM treatment and identifying sources of experimental variation would allow better comparisons across studies. In order to establish an optimal dosing regime for detecting experiment-dependent differences in tumorigenesis, we performed a dose curve analysis using AKR/J, SWR/J, and A/J mouse strains previously reported to vary widely in susceptibility to AOM. Although intraperitoneal or subcutaneous administration, but not in utero exposure, resulted in similar levels of tumor induction, significant dose- and strain-dependent effects of AOM were observed. No sex-dependent differences were observed. Increasing the number of treatments uncovered a significant strain-dependent effect on tumor promotion, independent of susceptibility to tumor initiation. Similarly, we used C57BL/6J and DBA/2J intercrosses to demonstrate that small diet modifications can significantly alter AOM-induced tumorigenesis in a background-dependent manner. These results provide experimental support for a standardized AOM treatment and for the importance of controlling both genetic and non-genetic factors when using this model.

Epiregulin is not essential for development of intestinal tumors but is required for protection from intestinal damage

Epiregulin, an epidermal growth factor family member, acts as a local signal mediator and shows dual biological activity, stimulating the proliferation of fibroblasts, hepatocytes, smooth muscle cells, and keratinocytes while inhibiting the growth of several tumor-derived epithelial cell lines. The epiregulin gene (Ereg) is located on mouse chromosome 5 adjacent to three other epidermal growth factor family members, epigen, amphiregulin, and betacellulin. Gene targeting was used to insert a lacZ reporter into the mouse Ereg locus and to ablate its function. Although epiregulin is broadly expressed and regulated both spatially and temporally, Ereg null mice show no overt developmental defects, reproductive abnormalities, or altered liver regeneration. Additionally, in contrast to previous hypotheses, Ereg deficiency does not alter intestinal cancer susceptibility, as assayed in the ApcMin model, despite showing robust expression in developing tumors. However, Ereg null mice are highly susceptible to cancer-predisposing intestinal damage caused by oral administration of dextran sulfate sodium.

Haploinsufficiency of p18(INK4c) sensitizes mice to carcinogen-induced tumorigenesis

The INK4 family of cyclin-dependent kinase (CDK) inhibitors negatively regulates cyclin D-dependent CDK4 and CDK6 and thereby retains the growth-suppressive function of Rb family proteins. Mutations in the CDK4 gene conferring INK4 resistance are associated with familial and sporadic melanoma in humans and result in a wide spectrum of tumors in mice. Whereas loss of function of other INK4 genes in mice leads to little or no tumor development, targeted deletion of p18(INK4c) causes spontaneous pituitary tumors and lymphoma late in life. Here we show that treatment of p18 null and heterozygous mice with a chemical carcinogen resulted in tumor development at an accelerated rate. The remaining wild-type allele of p18 was neither mutated nor silenced in tumors derived from heterozygotes. Hence, p18 is a haploinsufficient tumor suppressor in mice.

Airway surface liquid recovered by lavage with perfluorocarbon liquid in cats

BACKGROUND

Airway surface liquid (ASL) is difficult to sample. Lavage with an immiscible perfluorocarbon (PFC) liquid to recover ASL was evaluated in cats.

MATERIALS AND METHODS

Six wild-type cats underwent bronchoscopic lavage with a PFC (perfluorohexane), with the bronchoscope wedged in the feline equivalent of the right lower lobe. Two cats (control animals) were lavaged with a saline vehicle only. Four procedures were performed on each animal at 2-3-week intervals. Ionic composition of ASL was determined by flame photometry.

RESULTS

Cats lavaged with PFC showed significantly more acute respiratory distress than those lavaged with saline (respiratory rate following procedure: PFC, 47 +/- 5 min-1 vs. saline, 27 +/- 2 min-1, P < 0.05; O2 saturation: PFC 80 +/- 1% vs. saline, 91 +/- 1%, P < 0.01). The PFC group also had clinical evidence of chronic respiratory compromise (mean respiratory rate before next anaesthetic; PFC, 37 +/- 2 min-1 vs. saline, 20 +/- 3 min-1, P < 0.01). The PFC-lavaged lungs demonstrated persistent radiographic changes and histological evidence of small airways obstruction with distal alveolar damage. Six PFC lavages yielded ASL samples (> 100 microL) which were sufficient for analysis. Mean (+/- SEM) ionic concentrations in these samples were Na+ 157.4 +/- 14.5 mmol L-1, Cl- 150.5 +/- 16.8 mmol L-1 and K+ 10.1 +/- 1.7 mmol L-1.

CONCLUSIONS

Perfluorocarbon lavage can be used to collect unmodified ASL from the distal lung. However, repeated lavage with perfluorohexane was associated with significant pathological changes in this study.

Functional collaboration between different cyclin-dependent kinase inhibitors suppresses tumor growth with distinct tissue specificity

The presence of two families of seven distinct mammalian cyclin-dependent kinase (CDK) inhibitor genes is thought to mediate the complexity of connecting a variety of cellular processes to the cell cycle control pathway. The distinct pattern of tissue expression of CDK inhibitor genes suggests that they may function as tumor suppressors with different tissue specificities. To test this hypothesis, we have characterized two strains of double mutant mice lacking either p18(INK4c) and p27(KIP1) or p18(INK4c) and p21(CIP1/WAF1). Loss of both p18 and p27 function resulted in the spontaneous development by 3 months of age of at least eight different types of hyperplastic tissues and/or tumors in the pituitary, adrenals, thyroid, parathyroid, testes, pancreas, duodenum, and stomach. Six of these hyperplastic tissues and tumors were in endocrine organs, and several types of tumors routinely developed within the same animal, a phenotype reminiscent of that seen in combined human multiple endocrine neoplasia syndromes. The p18-p21 double null mice, on the other hand, developed pituitary adenomas, multifocal gastric neuroendocrine hyperplasia, and lung bronchioalveolar tumors later in life. G(1) CDK2 and CDK4 kinase activities were increased in both normal and neoplastic tissues derived from mice lacking individual CDK inhibitors and were synergistically stimulated by the simultaneous loss of two CDK inhibitors. This indicates that an increase in G(1) CDK kinase activity is a critical step during but is not sufficient for tumor growth. Our results suggest that functional collaborations between distinct CDK inhibitor genes are tissue specific and confer yet another level of regulation in cell growth control and tumor suppression.

Female mice heterozygous for IKK gamma/NEMO deficiencies develop a dermatopathy similar to the human X-linked disorder incontinentia pigmenti

IKK gamma/NEMO is the essential regulatory subunit of the I kappa B kinase (IKK), encoded by an X-linked gene in mice and humans. It is required for NF-kappa B activation and resistance to TNF-induced apoptosis. Female mice heterozygous for Ikk gamma/Nemo deficiency develop a unique dermatopathy characterized by keratinocyte hyperproliferation, skin inflammation, hyperkeratosis, and increased apoptosis. Although Ikk gamma+/- females eventually recover, Ikk gamma- males die in utero. These symptoms and inheritance pattern are very similar to those of incontinentia pigmenti (IP), a human genodermatosis, synthenic with the IKK gamma/NEMO locus. Indeed, biopsies and cells from IP patients exhibit defective IKK gamma/NEMO expression but normal expression of IKK catalytic subunits. This unique self-limiting disease, the first to be genetically linked to the IKK signaling pathway, is dependent on X-chromosome inactivation. We propose that the IKK gamma/NEMO-deficient cells trigger an inflammatory reaction that eventually leads to their death.

IL-2-deficient mice raised under germfree conditions develop delayed mild focal intestinal inflammation

Interleukin-2 (IL-2) amplifies immune stimuli and influences B cell differentiation. IL-2-deficient mice spontaneously develop intestinal inflammation if raised under specific pathogen-free (SPF) conditions. We quantitatively determined the aggressiveness and kinetics of gastrointestinal and hepatic inflammation in the presence or absence of viable bacteria in IL-2-deficient mice. Breeding colonies were maintained under SPF and germfree (GF) conditions. Intestinal tissues, serum, and mesenteric lymph nodes were obtained from mice at different ages for blind histological scoring, immunoglobulin measurements, mucosal T cell infiltration, and cytokine secretion. GF IL-2 -/- mice developed mild, focal, and nonlethal intestinal inflammation with delayed onset, whereas the more aggressive inflammation in SPF IL-2 -/- mice led to their death between 28 and 32 wk. Periportal hepatic inflammation was equal in the presence or absence of bacterial colonization. Intestinal immunoglobulin secretion decreased significantly by 13 wk of age in IL-2 -/- mice in both GF and SPF environments. In contrast to other genetically engineered rodents, IL-2 -/- mice develop mild focal gastrointestinal and active portal tract inflammation in the absence of viable bacteria.

CDK inhibitors p18(INK4c) and p27(Kip1) mediate two separate pathways to collaboratively suppress pituitary tumorigenesis

INK4 and CIP/KIP are two distinct families of cyclin-dependent kinase (CDK) inhibitors implicated in mediating a wide range of cell growth control signals. We have created p18(INK4c)-deficient mice. These mice develop gigantism and widespread organomegaly. The pituitary gland, spleen, and thymus are disproportionately enlarged and hyperplastic. T and B lymphocytes develop normally in p18-deficient mice, but both exhibit increased cellularity and a higher proliferative rate upon mitogenic stimulation. Loss of p18, like that of p27, but not other CDK inhibitor genes, leads to a gradual progression from intermediate lobe pituitary hyperplasia in young mice to an adenoma by 10 months of age with a nearly complete penetrance. Mice lacking both p18 and p27, like mice chimeric for Rb deficiency, invariably died from pituitary adenomas by 3 months. Hence, p18 and p27 mediate two separate pathways to collaboratively suppress pituitary tumorigenesis, likely by controlling the function of Rb.

Wild type p53 reduces the size of tumors caused by bovine leukemia virus-infected cells

Bat lung (BAT(2)CL6) cells infected with bovine leukemia virus (BLV) cause malignant tumors in nude mice that after 6 weeks subcutaneous growth, have an average volume of 0.3m(3). Uninfected bat lung cells (Tb 1 Lu) produce small benign neoplasms that average 0.003 cm(3). BAT(2)CL6 cells were transfected in vitro with expression vectors that produce wild type human or mutant p53. Production of human p53 in transfected BAT(2)CL6 cells was confirmed by immunoprecipitation of p53 and by immunohistochemical staining using anti-human p53 monoclonal antibodies. BAT(2)CL6 cells transfected with wild type p53 produced tumors in nude mice averaging 0.03 cm(3) whereas cells transfected with mutant p53 yielded tumors averaging 0.3cm(3). BAT(2)CL6 cell tumors after 1 week subcutaneous growth were transfected in situ with the wild type p53 gene. At 6 weeks tumor volume of in situ transfected tumors was similar to those resulting from cells transfected in vitro. Histopathologic examination and immunochemical staining of tumors produced in nude mice after wild type p53 treatment showed no significant differences when compared to tumors produced by untreated BAT(2)CL6 cells. Therefore, it is likely that the tumors produced by p53 treated-cells arose from cells that escaped transfection. The reduction of tumor size by restoration of wild type 53 may prove to be a useful therapy for BLV-induced tumors.

The mouse homolog of the Wiskott-Aldrich syndrome protein (WASP) gene is highly conserved and maps near the scurfy (sf) mutation on the X chromosome

The mouse WASP gene, the homolog of the gene mutated in Wiskott-Aldrich syndrome, has been isolated and sequenced. the predicted amino acid sequence is 86% identical to the human WASP sequence. A distinct feature of the mouse gene is an expanded polymorphic GGA trinucleotide repeat that codes for polyglycine and varies from 15 to 17 triplets in different Mus musculus strains. The genomic structure of the mouse WASP gene is expressed as an approximately 2.4-kb mRNA in thymus and spleen. Chromosomal mapping in an interspecific M. Musculus/M. spretus backcross placed the Wasp locus near the centromere of the mouse X chromosome, inseparable from Gata1, Tcfe3, and scurfy (sf). This localization makes Wasp a candidate for involvement in scurfy, a T cell-mediated fatal lymphoreticular disease of mice that has previously been proposed as a mouse homolog of Wiskott-Aldrich syndrome. Northern analysis of sf tissue samples indicated the presence of WASP mRNA in liver and skin, presumably as a consequence of lymphocytic infiltration, but non abnormalities in the amount or size of mRNA present.

Lymphotoxin-alpha-deficient mice. Effects on secondary lymphoid organ development and humoral immune responsiveness

Targeted mutagenesis in embryonic stem cells was used to generate mice deficient in lymphotoxin-alpha (LT-alpha). Mice lacking LT-alpha -/- (LT-alpha -/- mice) exhibit a phenotype dominated by defects in secondary lymphoid organ development. LT-alpha -/- mice lack lymph nodes and Peyer's patches, and possess spleens in which the usual architecture is disrupted. However, in a few of the mutants, abnormal lymph node-like structures were observed, mainly within the mesenteric fat. Abnormal clusters of lymphocytes were also found to accumulate in the periportal and perivascular regions of the liver and lung of LT-alpha -/- mice. Yet, lymphocytes from LT-alpha -/- mice appeared phenotypically normal, expressing the expected ratios of B and T cell surface markers as well as the lymphocyte homing marker, L-selectin. In addition, bone marrow cells from LT-alpha -/- mice were able to successfully reconstitute the lymphoid organs of severe combined immunodeficient mice. However, LT-alpha -/- mutant mice examined for humoral immune responsiveness were found to be impaired in their ability to respond to different Ag. These data illustrate the utility of this mouse model as a system for understanding lymphoid organ development and its effects on immune responsiveness.

Lymphotoxin-alpha-deficient mice. Effects on secondary lymphoid organ development and humoral immune responsiveness

Targeted mutagenesis in embryonic stem cells was used to generate mice deficient in lymphotoxin-alpha (LT-alpha). Mice lacking LT-alpha -/- (LT-alpha -/- mice) exhibit a phenotype dominated by defects in secondary lymphoid organ development. LT-alpha -/- mice lack lymph nodes and Peyer's patches, and possess spleens in which the usual architecture is disrupted. However, in a few of the mutants, abnormal lymph node-like structures were observed, mainly within the mesenteric fat. Abnormal clusters of lymphocytes were also found to accumulate in the periportal and perivascular regions of the liver and lung of LT-alpha -/- mice. Yet, lymphocytes from LT-alpha -/- mice appeared phenotypically normal, expressing the expected ratios of B and T cell surface markers as well as the lymphocyte homing marker, L-selectin. In addition, bone marrow cells from LT-alpha -/- mice were able to successfully reconstitute the lymphoid organs of severe combined immunodeficient mice. However, LT-alpha -/- mutant mice examined for humoral immune responsiveness were found to be impaired in their ability to respond to different Ag. These data illustrate the utility of this mouse model as a system for understanding lymphoid organ development and its effects on immune responsiveness.

Stabilization of the p53 gene product in two bovine leukemia virus infected cell lines

Fetal lamb kidney cells (FLK) and bat lung (BAT2CL6) cells that continuously produce bovine leukemia virus (BLV) were found to cause malignant tumors in nude mice. Uninfected bat lung cells (Tb 1 Lu) produced a small benign neoplasm. Pulse chase studies showed that the p53 gene product in BAT2CL6 cells was more stable compared with p53 in Tb 1 Lu cells. Mono-clonal antibody studies suggested that a mutant form of the p53 protein was produced in BLV-infected cells. Heteroduplex mapping studies of the p53 gene from BLV-infected cells also suggested that a mutation in p53 had occurred. Stabilization of the p53 gene product in BLV-infected cells may contribute to the progression of tumor virulence.

CD4+CD8- T cells are the effector cells in disease pathogenesis in the scurfy (sf) mouse

Mice hemizygous for the X-linked mutation, scurfy (sf), exhibit a fatal lymphoreticular disease that is mediated by T lymphocytes. To evaluate the respective roles of CD4 or CD8 single positive T cells in scurfy disease, neonates were treated with mAbs directed against the CD4 or CD8 molecules. Whereas mice treated with an anti-CD8 Ab developed lesions and succumbed to disease at the same time (17 days) as their untreated scurfy littermates, mice treated with an anti-CD4 Ab lived up to 11 wk before developing scurfy disease. To insure a more complete elimination of the T cell subsets, the scurfy mutation was bred onto beta 2-microglobulin (beta 2m)-deficient (CD8-less) and CD4-deficient transgenic mouse lines. Whereas there was little moderation of disease in beta 2m-deficient scurfy mice, CD4-deficient scurfy mice had markedly decreased scurfy lesions and a prolonged life span, similar to that of anti-CD4-treated sf/Y mice. Additionally, scurfy disease was transplanted into H-2-compatible nude mice through the adoptive transfer of CD4+CD8- T cells, but not CD4-CD8+ T cells. Flow-cytometric analysis revealed that sf/Y mice have an increased percentage of activated CD4+ T cells in their lymph nodes. In addition, there is an increase in the in vitro production of cytokines in the cultured splenocytes of CD8-less, but not CD4-less, scurfy mice. These data suggest that CD4+ T cells are critical mediators of disease in the scurfy mouse.

CD4+CD8- T cells are the effector cells in disease pathogenesis in the scurfy (sf) mouse

Mice hemizygous for the X-linked mutation, scurfy (sf), exhibit a fatal lymphoreticular disease that is mediated by T lymphocytes. To evaluate the respective roles of CD4 or CD8 single positive T cells in scurfy disease, neonates were treated with mAbs directed against the CD4 or CD8 molecules. Whereas mice treated with an anti-CD8 Ab developed lesions and succumbed to disease at the same time (17 days) as their untreated scurfy littermates, mice treated with an anti-CD4 Ab lived up to 11 wk before developing scurfy disease. To insure a more complete elimination of the T cell subsets, the scurfy mutation was bred onto beta 2-microglobulin (beta 2m)-deficient (CD8-less) and CD4-deficient transgenic mouse lines. Whereas there was little moderation of disease in beta 2m-deficient scurfy mice, CD4-deficient scurfy mice had markedly decreased scurfy lesions and a prolonged life span, similar to that of anti-CD4-treated sf/Y mice. Additionally, scurfy disease was transplanted into H-2-compatible nude mice through the adoptive transfer of CD4+CD8- T cells, but not CD4-CD8+ T cells. Flow-cytometric analysis revealed that sf/Y mice have an increased percentage of activated CD4+ T cells in their lymph nodes. In addition, there is an increase in the in vitro production of cytokines in the cultured splenocytes of CD8-less, but not CD4-less, scurfy mice. These data suggest that CD4+ T cells are critical mediators of disease in the scurfy mouse.

Transplantation of T cell-mediated, lymphoreticular disease from the scurfy (sf) mouse

The X-linked mutation, scurfy (sf), causes a fatal lymphoreticular disease characterized by runting, lymphadenopathy, splenomegaly, hypergammaglobulinemia, exfoliative dermatitis, Coombs'-positive anemia, and death by 24 days of age. T lymphocytes are required to mediate this syndrome as shown by a total absence of disease in mice bred to be scurfy and nude (sf/Y; nu/nu). The scurfy phenotype is not transmitted by sf/Y bone marrow transplants, though cells of scurfy origin do reconstitute all lymphoid organs in the recipient mouse. These data suggest that scurfy disease results from an abnormal T cell development process and not from an intrinsic stem cell defect. We therefore tested the ability of transplanted scurfy thymuses to transmit scurfy disease to congenic euthymic mice, to athymic (nude) mice, and to severe combined immunodeficiency (SCID) mice. Euthymic recipients of sf/Y thymic grafts remained clinically normal as did all SCID and nude recipients of normal thymus transplants. Morphological lesions similar to those found in scurfy mice occurred in all H-2-compatible nude and SCID recipients of sf/Y thymic grafts. Intraperitoneal injections of scurfy thymocytes, splenocytes, and lymph node cells also transmitted the scurfy phenotype to H-2-compatible nude mice and SCID mice. Our findings indicate that scurfy disease can be transmitted to T cell-deficient mice by engraftment of scurfy T cells, but that pathogenic scurfy T cell activities can be inhibited (or prevented) in immunocompetent recipient mice.

Candidate gene associated with a mutation causing recessive polycystic kidney disease in mice

A line of transgenic mice was generated that contains an insertional mutation causing a phenotype similar to human autosomal recessive polycystic kidney disease. Homozygotes displayed a complex phenotype that included bilateral polycystic kidneys and an unusual liver lesion. The mutant locus was cloned and characterized through use of the transgene as a molecular marker. Additionally, a candidate polycystic kidney disease (PKD) gene was identified whose structure and expression are directly associated with the mutant locus. A complementary DNA derived from this gene predicted a peptide containing a motif that was originally identified in several genes involved in cell cycle control.

Quantitative studies on CD4+ and CD8+ cytotoxic T lymphocyte responses against herpes simplex virus type 1 in normal and beta 2-m deficient mice

Against herpes simplex virus type 1 (HSV-1) infected target cells, effector T cells of both CD4- CD8+ and CD4+ CD8- phenotypes occur in both man and mice. In man, the CD4+ CD8- phenotype may dominate the response, but the situation in the mouse is unclear. In this report, several approaches are used to document the existence of HSV-1-specific cytotoxic T lymphocytes (CTL) of both phenotypes and to quantitate the frequency of their CTL precursors (CTL-p) in acutely HSV-1 infected animals. Evidence that CD4+ CD8- CTL occur was confirmed with beta 2-m- mice lacking CD8+ T cells and which generated CTL capable only of lysing MHC class II infected target cells. Comparisons of frequencies of CD4+ CD8- and CD4- CD8+ CTL-p showed the former to be 2-3-fold more frequent. The beta 2-m- mice generated only CD4+ CD8- CTL-p and their frequencies approximately equally the CD4+ CD8- CTL-p frequency in intact infected mice. Our results are discussed in terms of the value of the mouse model to study HSV-1 immunobiology.

Fatal lymphoreticular disease in the scurfy (sf) mouse requires T cells that mature in a sf thymic environment: potential model for thymic education

Characteristic lesions in mice hemi- or homozygous for the X-linked mutation scurfy (sf) include lymphohistiocytic proliferation in the skin and lymphoid organs, Coombs' test-positive anemia, hypergammaglobulinemia, and death by 24 days of age. The role of the thymus in the development of fatal lymphoreticular disease in the scurfy mouse was investigated. Neonatal thymectomy doubles the life span of scurfy mice, moderates the histologic lesions, and prevents anemia, despite the continued presence of high levels of serum IgG. Animals bred to be nude and scurfy (nu/nu; sf/Y) are viable, fertile, and free of scurfy lesions. Bone marrow from scurfy mice can reconstitute lethally irradiated, H-2-compatible animals but does not transmit scurfy disease. We conclude, from these data, that scurfy lesions are mediated by T lymphocytes that mature in an abnormal (sf) thymic environment.

X-linked lymphoreticular disease in the scurfy (sf) mutant mouse

Scurfy (sf) is a spontaneous, sex-linked, recessive mutation that maps to the extreme proximal portion of the X chromosome, about 2 centimorgans from sparse fur (spf). Hemizygotes for sf manifest several clinical disorders, evident at 14 days of age, including scaliness and crusting of the eyelids, ears, and tail, runting, reddening and swelling of the genital papilla, anemia, cachexia, and early death (average, 24 days). Our studies indicate that the phenotype of hemizygous scurfy is not, as has been suggested, a model for human X-linked ichthyosis, but appears to be a disease primarily affecting the lymphoreticular, and possibly the hematopoietic, systems. Gross lesions include marked splenomegaly, hepatomegaly, enlarged lymph nodes, and variable thickening of the ears. The characteristic histologic lesion is a lymphohistiocytic proliferation and infiltration of peripheral lymph nodes, spleen, liver, and skin. In routine hematoxylin and eosin-stained sections, these lesions efface lymph node architecture, thicken the dermis, and form nodular portal infiltrates in the liver. Scurfy lesions characteristically contain a population of large blastlike cells with round to oval nuclei, a vesicular chromatin pattern, and prominent single nucleoli. Mixed perivascular infiltrates of lymphocytes, macrophages, and granulocytes sometimes are found in kidney, heart, pancreas, lung, and mesenteries. There is excessive hematopoiesis in the liver and spleen. Cells expressing B220 or Thy-1 antigens localize to appropriate areas in the lymph nodes and spleen, but are rare in the portal infiltrates and are absent from the skin. There is a marked, polyclonal increase in serum IgG, severe Coombs'-positive anemia, and leukocytosis with atypical mononuclear cells. Scurfy mice are negative for antinuclear antibodies. Despite their morphologically aberrant lymphoreticular system, scurfy mice can exist in a conventional environment without evidence of opportunistic infection. Raising scurfy mice in a specific-pathogen-free environment does not alter disease expression. Thus, while our findings indicate that scurfy disease may be the result of immune dysfunction, it is not a classic immunodeficiency.

Bovine viral diarrhea virus-induced cerebellar disease in a calf

Bovine viral diarrhea virus (BVDV) was isolated from buffy coat cells of a 10-day-old calf with signs of cerebellar disease--ataxia, hypermetria, and intention head tremor. The tentative diagnosis was BVDV-induced cerebellar hypoplasia. At necropsy, gross lesions were not identified. Histologic findings suggested BVDV-induced diffuse hypomyelination throughout the CNS, as reported in the United Kingdom and The Netherlands.