Atrophy, oxidative switching and ultrastructural defects in skeletal muscle of the ataxia telangiectasia mouse model

Ataxia telangiectasia is a rare, multi system disease caused by ATM kinase deficiency. Atm-knockout mice recapitulate premature aging, immunodeficiency, cancer predisposition, growth retardation and motor defects, but not cerebellar neurodegeneration and ataxia. We explored whether Atm loss is responsible for skeletal muscle defects by investigating myofiber morphology, oxidative/glycolytic activity, myocyte ultrastructural architecture and neuromuscular junctions. Atm-knockout mice showed reduced muscle and fiber size. Atrophy, protein synthesis impairment and a switch from glycolytic to oxidative fibers were detected, along with an increase of in expression of slow and fast myosin types (Myh7, and Myh2 and Myh4, respectively) in tibialis anterior and solei muscles isolated from Atm-knockout mice. Transmission electron microscopy of tibialis anterior revealed misalignments of Z-lines and sarcomeres and mitochondria abnormalities that were associated with an increase in reactive oxygen species. Moreover, neuromuscular junctions appeared larger and more complex than those in Atm wild-type mice, but with preserved presynaptic terminals. In conclusion, we report for the first time that Atm-knockout mice have clear morphological skeletal muscle defects that will be relevant for the investigation of the oxidative stress response, motor alteration and the interplay with peripheral nervous system in ataxia telangiectasia

Anomalies in Dopamine Transporter Expression and Primary Cilium Distribution in the Dorsal Striatum of a Mouse Model of Niemann-Pick C1 Disease

The Niemann-Pick type C1 (NPC1) is a rare genetic disease characterized by the accumulation of endocytosed cholesterol and other lipids in the endosome/lysosome compartments. In the brain, the accumulation/mislocalization of unesterified cholesterol, gangliosides and sphingolipids is responsible for the appearance of neuropathological hallmarks, and progressive neurological decline in patients. The imbalance of unesterified cholesterol and other lipids, including GM2 and GM3 gangliosides, alters a number of signaling mechanisms impacting on the overall homeostasis of neurons. In particular, lipid depletion experiments have shown that lipid rafts regulate the cell surface expression of dopamine transporter (DAT) and modulate its activity. Dysregulated dopamine transporter’s function results in imbalanced dopamine levels at synapses and severely affects dopamine-induced locomotor responses and dopamine receptor-mediated synaptic signaling. Recent studies begin to correlate dopaminergic stimulation with the length and function of the primary cilium, a non-motile organelle that coordinates numerous signaling pathways. In particular, the absence of dopaminergic D2 receptor stimulation induces the elongation of dorso-striatal neuron’s primary cilia. This study has used a mouse model of the NPC1 disease to correlate cholesterol dyshomeostasis with dorso-striatal anomalies in terms of DAT expression and primary cilium (PC) length and morphology. We found that juvenile Npc1nmf164 mice display a reduction of dorso-striatal DAT expression, with associated alterations of PC number, length-frequency distribution, and tortuosity

Identification of the GlialCAM interactome: the G protein-coupled receptors GPRC5B and GPR37L1 modulate megalencephalic leukoencephalopathy proteins

Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC) is a type of vacuolating leukodystrophy, which is mainly caused by mutations in MLC1 or GLIALCAM. The two MLC-causing genes encode for membrane proteins of yet unknown function that have been linked to the regulation of different chloride channels such as the ClC-2 and VRAC. To gain insight into the role of MLC proteins, we have determined the brain GlialCAM interacting proteome. The proteome includes different transporters and ion channels known to be involved in the regulation of brain homeostasis, proteins related to adhesion or signaling as several G protein-coupled receptors (GPCRs), including the orphan GPRC5B and the proposed prosaposin receptor GPR37L1. Focusing on these two GPCRs, we could validate that they interact directly with MLC proteins. The inactivation of Gpr37l1 in mice upregulated MLC proteins without altering their localization. Conversely, a reduction of GPRC5B levels in primary astrocytes downregulated MLC proteins, leading to an impaired activation of ClC-2 and VRAC. The interaction between the GPCRs and MLC1 was dynamically regulated upon changes in the osmolarity or potassium concentration. We propose that GlialCAM and MLC1 associate with different integral membrane proteins modulating their functions and acting as a recruitment site for various signaling components as the GPCRs identified here. We hypothesized that the GlialCAM/MLC1 complex is working as an adhesion molecule coupled to a tetraspanin-like molecule performing regulatory effects through direct binding or influencing signal transduction events

A large scale hearing loss screen reveals an extensive unexplored genetic landscape for auditory dysfunction

The developmental and physiological complexity of the auditory system is likely reflected in the underlying set of genes involved in auditory function. In humans, over 150 non-syndromic loci have been identified, and there are more than 400 human genetic syndromes with a hearing loss component. Over 100 non-syndromic hearing loss genes have been identified in mouse and human, but we remain ignorant of the full extent of the genetic landscape involved in auditory dysfunction. As part of the International Mouse Phenotyping Consortium, we undertook a hearing loss screen in a cohort of 3006 mouse knockout strains. In total, we identify 67 candidate hearing loss genes. We detect known hearing loss genes, but the vast majority, 52, of the candidate genes were novel. Our analysis reveals a large and unexplored genetic landscape involved with auditory function

Effetti degli estrogeni e dei distruttori endocrini sulle cellule germinali embrionali di topo e sulle cellule somatiche della gonade

Negli ultimi anni si è assistito ad un crescente aumento nell’ambiente di sostanze che sono in grado di alterare il sistema endocrino poiché agiscono come l’ormone naturale estrogeno e per questo definite distruttori endocrini (EDs). Si ipotizza che l’esposizione agli EDs durante il periodo fetale e neo-natale sia la causa dell’insorgenza di numerosi disordini dell’apparato riproduttivo maschile come sterilità, cancro del testicolo, criptorchidismo e ipospadia che vengono definite con il termine unico di sindrome del testicolo disgenico (TDS). E’ importante studiare gli effetti degli estrogeni e degli xenoestrogeni, una classe di EDs, durante il periodo fetale ed in particolare durante lo sviluppo dell’apparto riproduttivo e conoscere i meccanismi, con cui tali sostanze esplicano i loro effetti. OBIETTIVI. Verificare l'espressione dei recettori degli estrogeni (ERs) nei precursori dei gameti adulti, ovvero nelle cellule germinali di topo denominate PGCs e analizzare i pathways molecolari attivati in queste cellule dagli estrogeni e dallo xenoestrogeno lindano. Inoltre si vuole verificare la presenza di ERs funzionali nelle cellule somatiche testicolari embrionali utilizzando costrutti ERE-luc e AP1-Luc per valutare l'attività estrogenica di xenoestrogeni. RISULTATI. Lo studio condotto in questa tesi mette in evidenza l'esistenza di pathways molecolari attivabili dall’estrogeno (E2) nelle gonadi embrionali di topo, in particolare, nel testicolo, sia nelle cellule germinali primordiali che nelle cellule somatiche. Abbiamo osservato che l’E2 è in grado di attivare, attraverso il recettore degli estrogeni ERα , importanti chinasi nelle PGCs (AKT, ERK1/2 e SRC) con effetti positivi sulla crescita e proliferazione di tali cellule. Si è osservato che il lindano, al contrario dell’E2, influenza negativamente la sopravvivenza di tali cellule attraverso una azione pro-apoptotica diretta, probabilmente derivante da effetti negativi sull’attività chinasica AKT. Inoltre abbiamo descritto per la prima volta l'esistenza di un recettore dell’estrogeno funzionale nelle cellule del Leydig testicolari durante lo stadio precoce dello sviluppo e messo a punto un test in vitro che può essere utilizzato per valutare l'attività estrogenica di xenoestrogeni direttamente sulle cellule del testicolo embrionale di mammiferi. CONCLUSIONI: Questi risultati rafforzano l’ipotesi dell’origine fetale della TDS. Numerosi studi hanno messo in evidenza gli effetti diretti degli estrogeni sul sistema endocrino, sull'espressione genica e su funzioni specifiche delle cellule somatiche testicolari embrionali, in particolare sulle cellule del Leydig, tuttavia tali studi sono carenti nelle cellule germinali. E’ importante conoscere i meccanismi di azione degli xenoestrogeni sullePGCs visto che attraverso esse viene trasmesso il genoma alle generazioni successive.In the recent years the increased presence of human made compounds that mimic the action of estrogens termed endocrine disrupters (ED) in environment and in food and the exposure to these compounds during fetal and neonatal period has been hypotized to be the cause of the raise of disorders of male reproductive function, such a decrease of sperm count, increase in the incidence of testicular cancer and cryptorchidism and hypospadias termed Testicular Dysgenesis Syndrome (TDS). For these reason, it is important to know how the estrogens and xenoestrogens, a class of ED, act during the fetal development and to know the mechanism by which these compounds exert their effects. AIMS: To study the expression of estrogen receptors (ERs) in the embryonic precursors of the adult gametes termed PGCs and to analyze the existence in such cells of intracellular molecular pathways modulable by estrogens and xenoestrogen lindane. To verify the presence of functional ER-beta in embryonic testicular somatic cells using an ERE-luc and AP1-Luc assay and to evaluate estrogenic activity of putative EDs on mammalian embryonic testis. RESULTS: The data described in this thesis highlights the existence of functional estrogen-dependent pathways in embryonic mouse gonads in particular in testis, both in germ and somatic cells. We found that E2 is able to activate via ER-beta multiple intracellular signalling in PGCs and that the xenoestrogens, lindane affect the survival in such cells through a direct pro-apoptotic action likely resulting from its adverse effect on AKT activity. Othermore, we described for the first time the existence of a functional ERα pathway in putative Leydig cells from early stage of testis development and describe an in vitro assay that can be used to evaluate estrogenic activity of compounds on mammalian embryonic testis. CONCLUSIONS: These results support the notion of the TDS origin during early stages of testis development. While data are accumulating showing direct effect of estrogens and EDs on gene expression and specific functions of somatic cells of the embryonic testes, in particular Leydig cells, such results on germ cells are lacking and further studies are needed to investigate the effects of these compounds on embryonic germ cell function including epigenetic regulation

Effetti degli estrogeni e dei distruttori endocrini sulle cellule germinali embrionali di topo e sulle cellule somatiche della gonade

Negli ultimi anni si è assistito ad un crescente aumento nell’ambiente di sostanze che sono in grado di alterare il sistema endocrino poiché agiscono come l’ormone naturale estrogeno e per questo definite distruttori endocrini (EDs). Si ipotizza che l’esposizione agli EDs durante il periodo fetale e neo-natale sia la causa dell’insorgenza di numerosi disordini dell’apparato riproduttivo maschile come sterilità, cancro del testicolo, criptorchidismo e ipospadia che vengono definite con il termine unico di sindrome del testicolo disgenico (TDS). E’ importante studiare gli effetti degli estrogeni e degli xenoestrogeni, una classe di EDs, durante il periodo fetale ed in particolare durante lo sviluppo dell’apparto riproduttivo e conoscere i meccanismi, con cui tali sostanze esplicano i loro effetti. OBIETTIVI. Verificare l'espressione dei recettori degli estrogeni (ERs) nei precursori dei gameti adulti, ovvero nelle cellule germinali di topo denominate PGCs e analizzare i pathways molecolari attivati in queste cellule dagli estrogeni e dallo xenoestrogeno lindano. Inoltre si vuole verificare la presenza di ERs funzionali nelle cellule somatiche testicolari embrionali utilizzando costrutti ERE-luc e AP1-Luc per valutare l'attività estrogenica di xenoestrogeni. RISULTATI. Lo studio condotto in questa tesi mette in evidenza l'esistenza di pathways molecolari attivabili dall’estrogeno (E2) nelle gonadi embrionali di topo, in particolare, nel testicolo, sia nelle cellule germinali primordiali che nelle cellule somatiche. Abbiamo osservato che l’E2 è in grado di attivare, attraverso il recettore degli estrogeni ERα , importanti chinasi nelle PGCs (AKT, ERK1/2 e SRC) con effetti positivi sulla crescita e proliferazione di tali cellule. Si è osservato che il lindano, al contrario dell’E2, influenza negativamente la sopravvivenza di tali cellule attraverso una azione pro-apoptotica diretta, probabilmente derivante da effetti negativi sull’attività chinasica AKT. Inoltre abbiamo descritto per la prima volta l'esistenza di un recettore dell’estrogeno funzionale nelle cellule del Leydig testicolari durante lo stadio precoce dello sviluppo e messo a punto un test in vitro che può essere utilizzato per valutare l'attività estrogenica di xenoestrogeni direttamente sulle cellule del testicolo embrionale di mammiferi. CONCLUSIONI: Questi risultati rafforzano l’ipotesi dell’origine fetale della TDS. Numerosi studi hanno messo in evidenza gli effetti diretti degli estrogeni sul sistema endocrino, sull'espressione genica e su funzioni specifiche delle cellule somatiche testicolari embrionali, in particolare sulle cellule del Leydig, tuttavia tali studi sono carenti nelle cellule germinali. E’ importante conoscere i meccanismi di azione degli xenoestrogeni sullePGCs visto che attraverso esse viene trasmesso il genoma alle generazioni successive.In the recent years the increased presence of human made compounds that mimic the action of estrogens termed endocrine disrupters (ED) in environment and in food and the exposure to these compounds during fetal and neonatal period has been hypotized to be the cause of the raise of disorders of male reproductive function, such a decrease of sperm count, increase in the incidence of testicular cancer and cryptorchidism and hypospadias termed Testicular Dysgenesis Syndrome (TDS). For these reason, it is important to know how the estrogens and xenoestrogens, a class of ED, act during the fetal development and to know the mechanism by which these compounds exert their effects. AIMS: To study the expression of estrogen receptors (ERs) in the embryonic precursors of the adult gametes termed PGCs and to analyze the existence in such cells of intracellular molecular pathways modulable by estrogens and xenoestrogen lindane. To verify the presence of functional ER-beta in embryonic testicular somatic cells using an ERE-luc and AP1-Luc assay and to evaluate estrogenic activity of putative EDs on mammalian embryonic testis. RESULTS: The data described in this thesis highlights the existence of functional estrogen-dependent pathways in embryonic mouse gonads in particular in testis, both in germ and somatic cells. We found that E2 is able to activate via ER-beta multiple intracellular signalling in PGCs and that the xenoestrogens, lindane affect the survival in such cells through a direct pro-apoptotic action likely resulting from its adverse effect on AKT activity. Othermore, we described for the first time the existence of a functional ERα pathway in putative Leydig cells from early stage of testis development and describe an in vitro assay that can be used to evaluate estrogenic activity of compounds on mammalian embryonic testis. CONCLUSIONS: These results support the notion of the TDS origin during early stages of testis development. While data are accumulating showing direct effect of estrogens and EDs on gene expression and specific functions of somatic cells of the embryonic testes, in particular Leydig cells, such results on germ cells are lacking and further studies are needed to investigate the effects of these compounds on embryonic germ cell function including epigenetic regulation

Mouse Mutants of Gpr37 and Gpr37l1 Receptor Genes: Disease Modeling Applications

The vertebrate G protein–coupled receptor 37 and G protein–coupled receptor 37-like 1 (GPR37 and GPR37L1) proteins have amino acid sequence homology to endothelin and bombesin-specific receptors. The prosaposin glycoprotein, its derived peptides, and analogues have been reported to interact with and activate both putative receptors. The GPR37 and GPR37L1 genes are highly expressed in human and rodent brains. GPR37 transcripts are most abundant in oligodendrocytes and in the neurons of the substantia nigra and hippocampus, while the GPR37L1 gene is markedly expressed in cerebellar Bergmann glia astrocytes. The human GPR37 protein is a substrate of parkin, and its insoluble form accumulates in brain samples from patients of inherited juvenile Parkinson’s disease. Several Gpr37 and Gpr37l1 mouse mutant strains have been produced and applied to extensive in vivo and ex vivo analyses of respective receptor functions and involvement in brain and other organ pathologies. The genotypic and phenotypic characteristics of the different mouse strains so far published are reported and discussed, and their current and proposed applications to human disease modeling are highlighted