Carbonic Anhydrase 2 Deletion Delays the Growth of Kidney Cysts Whereas Foxi1 Deletion Completely Abrogates Cystogenesis in TSC.

Tuberous sclerosis complex (TSC) presents with renal cysts and benign tumors, which eventually lead to kidney failure. The factors promoting kidney cyst formation in TSC are poorly understood. Inactivation of carbonic anhydrase 2 (Car2) significantly reduced, whereas, deletion of Foxi1 completely abrogated the cyst burden in Tsc1 KO mice. In these studies, we contrasted the ontogeny of cyst burden in Tsc1/Car2 dKO mice vs. Tsc1/Foxi1 dKO mice. Compared to Tsc1 KO, the Tsc1/Car2 dKO mice showed few small cysts at 47 days of age. However, by 110 days, the kidneys showed frequent and large cysts with overwhelming numbers of A-intercalated cells in their linings. The magnitude of cyst burden in Tsc1/Car2 dKO mice correlated with the expression levels of Foxi1 and was proportional to mTORC1 activation. This is in stark contrast to Tsc1/Foxi1 dKO mice, which showed a remarkable absence of kidney cysts at both 47 and 110 days of age. RNA-seq data pointed to profound upregulation of Foxi1 and kidney-collecting duct-specific H+-ATPase subunits in 110-day-old Tsc1/Car2 dKO mice. We conclude that Car2 inactivation temporarily decreases the kidney cyst burden in Tsc1 KO mice but the cysts increase with advancing age, along with enhanced Foxi1 expression.

Review of the spectrum of tuberous sclerosis complex: The Saudi Arabian Experience.

OBJECTIVES: To determine the prevalence of tuberous sclerosis complex (TSC) in the paediatric Saudi population and to characterise the range of clinical symptoms, neurocutaneous findings, neuroimaging results, and complications of the disease. METHODS: A total of 61 genetically confirmed TSC patients from the National Guard Health Affairs (NGHA) in Saudi Arabia were the subject of this retrospective descriptive analysis. The data were presented using descriptive measures. RESULTS: The mean age at diagnosis was found to be 4.9 years. Subependymal nodules (86.9%), numerous cortical tubers and/or radial migration lines (63.9%), and hypomelanotic macules (63.9%) were the 3 most common significant criteria. The vast majority (86.9%) of those diagnosed had epilepsy, of which 50% were considered medically intractable. Nearly half of our subjects underwent genetic testing, which revealed that TSC2 predominated over TSC1. Symptoms of Tuberous Sclerosis Complex-Associated Neuropsychiatric Disorders (TAND) were present in 66.7% of TSC1 patients and 73.9% of TSC2 patients. CONCLUSION: The findings of this study demonstrate that the clinical spectrum of TSC among Saudi children is consistent with the body of existing literature. The TSC2 was more prevalent than TSC1. The most frequent signs were cutaneous and neurological. Monitoring TSC patients regularly is crucial to identify any issues as soon as possible.

Research of the unrecognised functions of miR-375 in prostate cancer cells.

Many cancers, including prostate cancer, have miRNAs with altered expression levels. These miRNAs play a pivotal role in regulating cancer initiation, invasion, and metastasis. miRNAs are an important component in cancer diagnosis and therapy and can play a key role as biomarkers or chemotherapeutic agents.  This investigation aimed to show the effects of miR-375 on PCa. In this project, target prediction tools and the KEGG pathway were performed to determine the potential targets of miR-375. Transfection was performed using miR-375 mimic and inhibitor. The actions of miRNAs on cell viability and migration were examined in PCa cells. In addition, qRT-PCR was executed to evaluate changes in gene expression in the PI3K-mTOR pathway. The analyses exposed that the upregulation of miR-375 repressed the viability at 48 h. While stimulation of miR-375 did not repress the migration, suppression of miR-375 reduced the migration at 24 and 48 hours. The predicted target TSC1 gene is not directly targeted by miR-375. Interestingly, in response to PIK3CA increase, mTOR expression was suppressed in all cells except LNCAP cells. In conclusion, miR-375 has anti-proliferative and cell migration inhibitory effects in prostate cancer. However, studies demonstrate that miR-375 may have tumor suppressor and oncogenic effects when considering cell molecular differences.

The autophagy-mediated mechanism via TSC1/mTOR signaling pathway in thiram-induced tibial dyschondroplasia of broilers.

Thiram is a member of the dithiocarbamate family and is widely used in agriculture, especially in low-income countries. Its residues lead to various diseases, among which tibial dyschondroplasia (TD) in broiler chickens is the most common. Recent studies have also demonstrated that thiram residues may harm human health. Our previous study showed that the activity of the mTOR (mammalian target of rapamycin) signaling pathway has changed after thiram exposure. In the current study, we investigated the effect of autophagy via the mTOR signaling pathway after thiram exposure in vitro and in vivo. Our results showed that thiram inhibited the protein expression of mTOR signaling pathway-related genes such as p-4EBP1 and p-S6K1. The analysis showed a significant increase in the expression of key autophagy-related proteins, including LC3, ULK1, ATG5, and Beclin1. Further investigation proved that the effects of thiram were mediated through the downregulation of mTOR. The mTOR agonist MHY-1485 reverse the upregulation of autophagy caused by thiram in vitro. Moreover, our experiment using knockdown of TSC1 resulted in chondrocytes expressing lower levels of autophagy. In conclusion, our results demonstrate that thiram promotes autophagy via the mTOR signaling pathway in chondrogenesis, providing a potential pharmacological target for the prevention of TD.

A large deletion in TSC2 causes tuberous sclerosis complex by dysregulating PI3K/AKT/mTOR signaling pathway.

BACKGROUND/AIM: Tuberous sclerosis complex (TSC) is a multi-system syndrome caused by loss-of-function mutation in TSC1 or TSC2. Most TSC patients present with cardiac rhabdomyoma or cortical tubers during fetal life, and the symptoms are not uniform as their age. The gene products of TSC1/2 are components of the TSC protein complex and are important role in the PI3K/AKT/mTOR (PAM) signaling pathway. Based on three members of a family with variable expressivity, the purpose of this study was to clarify the clinical features of TSC in different age groups and to analyze the genetic characteristics of TSC2 gene. METHODS: Clinical exome sequencing and co-segregation were used to identify a three-generation family with four affected individuals. HEK-293T cell model was constructed for subsequent experiments. Quantitative RT-PCR, western blotting, and subcellular localization were used to analyze the expression effect of TSC2 mutation. CCK-8 assay, wound healing assay, and cell cycle analysis were used to analyze the function effect of TSC2 mutation. RESULT: We identified a TSC family with heterozygous deletion of exon 4 in TSC2 by clinical exon sequencing. Sanger sequencing indicated that the affected individuals have 2541-bp deletion that encompassed exon 4 and adjacent introns. Deletion of exon 4 decreased the TSC2 mRNA and protein levels in HEK-293T cells, and activated the PI3K/AKT/mTOR pathway, thereby altering the cell cycle and promoting cell proliferation and migration. CONCLUSION: We confirmed the pathogenicity of the large deletion in TSC2 in a three- generations family.. Deletion of exon 4 of TSC2 affected cell proliferation, migration, and cell cycle via abnormal activation of the PAM pathway. This study evaluated the pathogenic effect of deletion of exon 4 of TSC2 and investigated the underlying mechanism.

Identification of a complex intrachromosomal inverted insertion in the long arm of chromosome 9 as a cause of tuberous sclerosis complex in a Korean family.

BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder, caused by a loss-of-function of either TSC1 or TSC2 gene. However, in 10%-15% TSC patients there is no pathogenic variant identified in either TSC1 or TSC2 genes based on standard clinical testing. METHODS: In this study, genome sequencing was performed for families with clinical diagnosis of TSC with negative results from TSC1 and TSC2 single-gene tests. RESULTS: Herein, we report a family presenting a classical TSC phenotype with an unusual, complex structural variant involving the TSC1 gene: an intrachromosomal inverted insertion in the long arm of chromosome 9. We speculate that the inverted 9q33.3q34.13 region was inserted into the q31.2 region with the 3'-end of the breakpoint of the inversion being located within the TSC1 gene, resulting in premature termination of TSC1. CONCLUSIONS: In this study, we demonstrate the utility of genome sequencing for the identification of complex chromosomal rearrangement. Because the breakpoints are located within the deep intronic/intergenic region, this copy-neutral variant was missed by the TSC1 and TSC2 single-gene tests and contributed to an unknown etiology. Together, this finding suggests that complex structural variants may be underestimated causes for the etiology of TSC.

Cerebral vascular and blood brain-barrier abnormalities in a mouse model of epilepsy and tuberous sclerosis complex.

OBJECTIVE: Tuberous sclerosis complex (TSC) is a genetic disorder, characterized by tumor formation in the brain and other organs, and severe neurological symptoms, such as epilepsy. Abnormal vascular endothelial growth factor (VEGF) expression may promote angiogenesis in kidney and lung tumors in TSC and has been identified in brain specimens from TSC patients, but the role of VEGF and vascular abnormalities in neurological manifestations of TSC is poorly defined. In this study, we investigated abnormalities in brain VEGF expression, cerebral blood vessel anatomy, and blood-brain barrier (BBB) structure and function in a mouse model of TSC. METHODS: Tsc1GFAP CKO mice were used to investigate VEGF expression and vascular abnormalities in the brain by Western blotting and immunohistochemical analysis of vascular and BBB markers. In vivo two-photon imaging was used to assess BBB permeability to normally impenetrable fluorescently labeled compounds. The effect of mechanistic target of rapamycin (mTOR) pathway inhibitors, VEGF receptor antagonists (apatinib), or BBB stabilizers (RepSox) was assessed in some of these assays, as well as on seizures by video-electroencephalography. RESULTS: VEGF expression was elevated in cortex of Tsc1GFAP CKO mice, which was reversed by the mTOR inhibitor rapamycin. Tsc1GFAP CKO mice exhibited increased cerebral angiogenesis and vascular complexity in cortex and hippocampus, which were reversed by the VEGF receptor antagonist apatinib. BBB permeability was abnormally increased and BBB-related tight junction proteins occludin and claudin-5 were decreased in Tsc1GFAP CKO mice, also in an apatinib- and RepSox-dependent manner. The BBB stabilizer (RepSox), but not the VEGF receptor antagonist (apatinib), decreased seizures and improved survival in Tsc1GFAP CKO mice. SIGNIFICANCE: Increased brain VEGF expression is dependent on mTOR pathway activation and promotes cerebral vascular abnormalities and increased BBB permeability in a mouse model of TSC. BBB modulation may affect epileptogenesis and represent a rational treatment for epilepsy in TSC.

Reprogramming tumor-associated macrophages to outcompete endovascular endothelial progenitor cells and suppress tumor neoangiogenesis.

Tumors develop by invoking a supportive environment characterized by aberrant angiogenesis and infiltration of tumor-associated macrophages (TAMs). In a transgenic model of breast cancer, we found that TAMs localized to the tumor parenchyma and were smaller than mammary tissue macrophages. TAMs had low activity of the metabolic regulator mammalian/mechanistic target of rapamycin complex 1 (mTORC1), and depletion of negative regulator of mTORC1 signaling, tuberous sclerosis complex 1 (TSC1), in TAMs inhibited tumor growth in a manner independent of adaptive lymphocytes. Whereas wild-type TAMs exhibited inflammatory and angiogenic gene expression profiles, TSC1-deficient TAMs had a pro-resolving phenotype. TSC1-deficient TAMs relocated to a perivascular niche, depleted protein C receptor (PROCR)-expressing endovascular endothelial progenitor cells, and rectified the hyperpermeable blood vasculature, causing tumor tissue hypoxia and cancer cell death. TSC1-deficient TAMs were metabolically active and effectively eliminated PROCR-expressing endothelial cells in cell competition experiments. Thus, TAMs exhibit a TSC1-dependent mTORC1-low state, and increasing mTORC1 signaling promotes a pro-resolving state that suppresses tumor growth, defining an innate immune tumor suppression pathway that may be exploited for cancer immunotherapy.

Identification of genetic variants in two families with Keratoconus.

BACKGROUND: This research investigated the genetic characteristic of two Chinese families with keratoconus (KC). METHODS: For all people in the two families with KC, their history, clinical data, and peripheral blood were collected. One hundred healthy participants without KC and 112 sporadic KC patients were recruited as the controls. Whole exome sequencing of the genomic DNA and polymerase chain reaction were conducted for all the controls and family members to verify the variants. Functional analyses of the variants was performed using the software programs. RESULTS: A missense tuberous sclerosis 1 (TSC1) variant g.135797247A > G (c.622A > G, p.Ser208Gly) was detected in family 1. A single nucleotide polymorphism (SNP) rs761232139 (p.Gly235Arg) in aldehyde dehydrogenase 3 family member A1 (ALDH3A1) gene was detected in family 2. The variant c.622A > G in TSC1 and the SNP rs761232139 in ALDH3A1 were predicted as being probably damaging. CONCLUSIONS: Novel variant c.622A > G in TSC1 and SNP rs761232139 in ALDH3A1 have been detected in families with KC. These two findings may play a role in the pathogenesis of KC.

Sclerotic Bone Lesions as a Clue in the Diagnosis of Three Generations of Tuberous Sclerosis Complex: Case Report and Review of Literature.

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder that can involve multiple organ systems. Diagnosis is based on independent clinical diagnostic criteria and genetic diagnostic criteria (pathogenic variants on TSC1 and TSC2 genes). To make a definitive diagnosis can be especially difficult in oligosymptomatic or asymptomatic patients and in those patients with genetic variants of uncertain significance (VUS). Early diagnosis and lifelong surveillance are paramount to avoid morbidity and potentially life-threatening complications. To increase diagnostic sensibility, less known manifestations of TSC can be helpful. Herein we show a case in which SBLs were used as a diagnostic clue to help diagnose three generations of oligosymptomatic TSC carrying a VUS in TSC1. SBLs are commonly detected in imaging studies of patients with TSC and have been recently included as a minor clinical diagnostic criterion. Clinicians and radiologists should be aware of their significance as they can be mistaken with osteoblastic metastases.

Establishment of human induced pluripotent stem cell lines, KMUGMCi006, from a patient with Tuberous sclerosis complex (TSC) bearing mosaic nonsense mutations in the Tuberous sclerosis complex 2 (TSC2) gene.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by neuropsychiatric symptoms and multiple dysplastic organ lesions, caused by loss of function mutations in either TSC1 or TSC2. The peripheral blood mononuclear cells (PBMCs) from a patient carrying mosaic nonsense mutation of TSC2 gene were reprogrammed using the CytoTune-iPS2.0 Sendai Reprogramming Kit. The human induced pluripotent cell (hiPSC) lines with the mutation and without the mutation were established. The heterozygous nonsense mutation in TSC2 will cause the truncated protein, which is known to associated with TSC. The established hiPSC lines will enable proper in vitro disease modelling of TSC.

An Integral Approach to the Molecular Diagnosis of Tuberous Sclerosis Complex: The Role of Mosaicism and Splicing Variants.

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder characterized by the presence of hamartomas in multiple organs. At the molecular level, the disease is caused by pathogenic variants in the TSC1 and TSC2 genes, and only 10% to 25% of clinically diagnosed patients remain negative after multiplex ligation-dependent probe amplification and exon sequencing of both genes. Here, to improve the molecular diagnosis of TSC, we developed an integral approach that includes multiplex ligation-dependent probe amplification and deep-coverage next-generation sequencing of the entire TSC1 and TSC2 genes, along with an adapted bioinformatic pipeline to detect variants at low allele frequencies (>1%). Using this workflow, the molecular cause was identified in 29 of 42 patients with TSC, describing here, for the first time, 12 novel pathogenic variants in TSC genes. These variants included seven splicing variants, five of which were studied at the cDNA level, determining their effect on splicing. In addition, 8 of the 29 pathogenic variants were detected in mosaicism, including four patients with previous negative study results who presented extremely low mosaic variants (allele frequency, <16%). We demonstrate that this integral approach allows the molecular diagnosis of patients with TSC and improves the conventional one by adapting the technology to the detection of low-frequency mosaics.

Comprehensive genetic and phenotype analysis of 95 individuals with mosaic tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is a neurogenetic disorder due to loss-of-function TSC1 or TSC2 variants, characterized by tumors affecting multiple organs, including skin, brain, heart, lung, and kidney. Mosaicism for TSC1 or TSC2 variants occurs in 10%-15% of individuals diagnosed with TSC. Here, we report comprehensive characterization of TSC mosaicism by using massively parallel sequencing (MPS) of 330 TSC samples from a variety of tissues and fluids from a cohort of 95 individuals with mosaic TSC. TSC1 variants in individuals with mosaic TSC are much less common (9%) than in germline TSC overall (26%) (p < 0.0001). The mosaic variant allele frequency (VAF) is significantly higher in TSC1 than in TSC2, in both blood and saliva (median VAF: TSC1, 4.91%; TSC2, 1.93%; p = 0.036) and facial angiofibromas (median VAF: TSC1, 7.7%; TSC2 3.7%; p = 0.004), while the number of TSC clinical features in individuals with TSC1 and TSC2 mosaicism was similar. The distribution of mosaic variants across TSC1 and TSC2 is similar to that for pathogenic germline variants in general TSC. The systemic mosaic variant was not present in blood in 14 of 76 (18%) individuals with TSC, highlighting the value of analysis of multiple samples from each individual. A detailed comparison revealed that nearly all TSC clinical features are less common in individuals with mosaic versus germline TSC. A large number of previously unreported TSC1 and TSC2 variants, including intronic and large rearrangements (n = 11), were also identified.

Tuberous Sclerosis Complex Kidney Lesion Pathogenesis: A Developmental Perspective.

The phenotypic diversity of tuberous sclerosis complex (TSC) kidney pathology is enigmatic. Despite a well-established monogenic etiology, an incomplete understanding of lesion pathogenesis persists. In this review, we explore the question: How do TSC kidney lesions arise? We appraise literature findings in the context of mutational timing and cell-of-origin. Through a developmental lens, we integrate the critical results from clinical studies, human specimens, and genetic animal models. We also review novel insights gleaned from emerging organoid and single-cell sequencing technologies. We present a new model of pathogenesis which posits a phenotypic continuum, whereby lesions arise by mutagenesis during development from variably timed second-hit events. This model can serve as a conceptual framework for testing hypotheses of TSC lesion pathogenesis, both in the kidney and in other affected tissues.

Pathogenic RHEB Somatic Variant in a Child With Tuberous Sclerosis Complex Without Pathogenic Variants in TSC1 or TSC2.

OBJECTIVE: To describe a child meeting diagnostic criteria for tuberous sclerosis complex (TSC) carrying a pathogenic somatic variant in RHEB, but no pathogenic variants in the 2 known TSC genes, TSC1 or TSC2. METHODS: We present the clinical and imaging findings in a child presenting with drug-resistant focal seizures and multiple cortical tubers, a subependymal giant cell astrocytoma and multiple subependymal nodules in 1 cerebral hemisphere. Targeted panel sequencing and exome sequencing were performed on genomic DNA derived from blood and resected tuber tissue. RESULTS: The child satisfied clinical diagnostic criteria for TSC, having 3 major features, only 2 of which are required for diagnosis. Genetic testing did not identify pathogenic variants or copy number variations in TSC1 or TSC2 but identified a pathogenic somatic RHEB variant (NM_005614.4:c.104_105delACinsTA [p.Tyr35Leu]) in the cortical tuber. DISCUSSION: RHEB is a partner of the TSC1/2 complex in the mechanistic target of rapamycin pathway. Somatic variants in RHEB are associated with focal cortical dysplasia and hemimegalencephaly. We propose that variants in RHEB may explain some of the genetically undiagnosed TSC cases and may be the third gene for TSC, or TSC3.

Reprint of: lessons from histopathologic examination of nephrectomy specimens in patients with tuberous sclerosis complex: cysts, angiomyolipomas & renal cell carcinoma.

Renal manifestations in patients with tuberous sclerosis complex (TSC) include cysts, angiomyolipoma, and renal cell carcinoma. Unlike many hereditary predisposition syndromes, the spectrum of renal tumors in TSC patients (including both angiomyolipoma and renal cell carcinoma) is broad, with significant morphologic heterogeneity. An improved understanding of histopathologic findings in TSC patients and associated clinicopathologic correlates has significant implications not just in establishing a diagnosis of TSC, but also in the recognition of sporadic tumors occurring secondary to somatic alterations of TSC1/TSC2/MTOR pathway genes and accurate prognostication. In this review, we have discussed issues relevant to clinical management based on histopathologic findings in nephrectomy specimens from patients with TSC. This includes discussions related to screening for TSC, diagnosis of PKD1/TSC2 contiguous gene deletion syndrome, the morphologic spectrum of angiomyolipoma and renal epithelium-derived neoplasia, including the risk of disease progression.

Tsc2 mutation rather than Tsc1 mutation dominantly causes a social deficit in a mouse model of tuberous sclerosis complex.

BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that is associated with neurological symptoms, including autism spectrum disorder. Tuberous sclerosis complex is caused by pathogenic germline mutations of either the TSC1 or TSC2 gene, but somatic mutations were identified in both genes, and the combined effects of TSC1 and TSC2 mutations have been unknown. METHODS: The present study investigated social behaviors by the social interaction test and three-chambered sociability tests, effects of rapamycin treatment, and gene expression profiles with a gene expression microarray in Tsc1 and Tsc2 double heterozygous mutant (TscD+/-) mice. RESULTS: TscD+/- mice exhibited impairments in social behaviors, and the severity of impairments was similar to Tsc2+/- mice rather than Tsc1+/- mice. Impairments in social behaviors were rescued by rapamycin treatment in all mutant mice. Gene expression profiles in the brain were greatly altered in TscD+/- mice more than in Tsc1+/- and Tsc2+/- mice. The gene expression changes compared with wild type (WT) mice were similar between TscD+/- and Tsc2+/- mice, and the overlapping genes whose expression was altered in mutant mice compared with WT mice were enriched in the neoplasm- and inflammation-related canonical pathways. The "signal transducer and activator of transcription 3, interferon regulatory factor 1, interferon regulatory factor 4, interleukin-2R α chain, and interferon-γ" signaling pathway, which is initiated from signal transducer and activator of transcription 4 and PDZ and LIM domain protein 2, was associated with impairments in social behaviors in all mutant mice. LIMITATIONS: It is unclear whether the signaling pathway also plays a critical role in autism spectrum disorders not caused by Tsc1 and Tsc2 mutations. CONCLUSIONS: These findings suggest that TSC1 and TSC2 double mutations cause autistic behaviors similarly to TSC2 mutations, although significant changes in gene expression were attributable to the double mutations. These findings contribute to the knowledge of genotype-phenotype correlations in TSC and suggest that mutations in both the TSC1 and TSC2 genes act in concert to cause neurological symptoms, including autism spectrum disorder.

Refractive Errors, Retinal Findings, and Genotype of Tuberous Sclerosis Complex: A Retrospective Cohort Study.

PURPOSE: To examine the refractive errors, retinal manifestations, and genotype in tuberous sclerosis complex (TSC) patients in a Korean population. MATERIALS AND METHODS: A total of 98 patients with TSC were enrolled in Severance Hospital for a retrospective cohort study. The number of retinal astrocytic hamartoma and retinal achromic patch within a patient, as well as the size, bilaterality, and morphological type were studied. In addition, the refractive status of patients and the comorbidity of intellectual disability and epilepsy were also examined. RESULTS: Retinal astrocytic hamartoma was found in 37 patients, and bilateral invasion was observed in 20 patients (54%). TSC1 mutation was associated with myopia (p=0.01), while TSC2 mutation was associated with emmetropia (p=0.01). Retinal astrocytic hamartoma was categorized into three morphological types and examined as follows: type I (87%), type II (35%), and type III (14%). Single invasion of retinal astrocytic hamartoma was identified in 32% of the patients, and multiple invasions in 68%. The TSC1/TSC2 detection rate was 91% (41/45). Among them, TSC1 variant was detected in 23 patients (54%), whereas TSC2 variant was detected in 18 patients (40%). The results showed that TSC2 mutations are correlated with a higher rate of retinal astrocytic hamartoma involvement (all p<0.05), and multiple and bilateral involvement of retinal hamartomas (all p<0.05). However, the size of retinal astrocytic hamartomas, comorbidity of epilepsy, or intellectual disability did not show correlation with the genetic variant. CONCLUSION: TSC1 variant patients were more myopic, while TSC2 variant patients showed association with more extensive involvement of retinal astrocytic hamartoma.

Off-target activity of the 8 kb Dmp1-Cre results in the deletion of Tsc1 gene in mouse intestinal mesenchyme.

The Dmp1-Cre mouse, expressing Cre from an 8-kb DNA fragment of the mouse Dmp1 gene, is a common tool to study gene functions in osteocytes. Here we report that the deletion of Tsc1 (TSC complex subunit 1) by 8 kb Dmp1-Cre causes rectal prolapse in mice. Histological examination shows the presence of colon polyps in Tsc1-deficient mice in association with significantly larger colon and narrower lumen, which recapitulates the common polyps pathology in Tuberous Sclerosis, an autosomal dominant disorder caused by mutations in either TSC1 or TSC2. The intestine in Tsc1-deficient mice is also enlarged with the presence of taller villi. Using the Ai14 reporter mice that express a red fluorescence protein upon Cre recombination, we show that 8 kb Dmp1-Cre activity is evident in portion of the mesenchyme of the colon and small intestine. Lastly, our data show that Tsc1 deletion by Dmp1-Cre leads to an increased proliferation in the mesenchyme of colon, which at least partly contributes to the polyps pathology seen in this mouse model and is likely a contributing factor of the polyps in Tuberous Sclerosis.