Biomedical subjects

Jun Aruga

Publications and source records attributed to Jun Aruga.

17 recordsLinked to original sources

PubMed2006

Comparative analysis of structure, expression and PSD95-binding capacity of Lrfn, a novel family of neuronal transmembrane proteins.

Leucine-rich repeat and fibronectin III domain-containing (Lrfn) has five members in mouse and human (Lrfn1, Lrfn2, Lrfn3, Lrfn4, Lrfn5), and homologues in other vertebrates. Lrfn proteins share leucine-rich repeat (LRR)-immunoglobulin-like (Ig)-fibronectin type III (Fn)-transmembrane domain structure, which is also found in LRR-Ig-Fn superfamily proteins. Mouse Lrfn genes were expressed at adult stage predominantly in the brain. In the course of development, expression of Lrfn1, Lrfn3, and Lrfn4 started from immature neural cells, whereas that of Lrfn2 and Lrfn5 was limited to mature ones. Lrfn1-5 commonly encode glycoproteins spanning the plasma membrane, with their N-terminus located on the extracellular side. C-termini of Lrfn1, Lrfn2 and Lrfn4 were bound by PDZ domains of postsynaptic protein PSD95, re-distributing PSD95 to cell periphery where the Lrfn proteins were detected. These results suggest that Lrfn proteins are neuronal components with a role in the developing or mature vertebrate nervous system.

Amino Acid Sequence↗

PubMed2006

A wide-range phylogenetic analysis of Zic proteins: implications for correlations between protein structure conservation and body plan complexity.

We compared Zic homologues from a wide range of animals. Striking conservation was found in the zinc finger domains, in which an exon-intron boundary has been kept in all bilateralians but not cnidarians, suggesting that all of the bilateralian Zic genes are derived from a single gene in a bilateralian ancestor. There were additional conserved amino acid sequences, ZOC and ZF-NC. Combined analysis of the zinc finger, ZOC, and ZF-NC revealed the presence of two classes of Zic, based on the degree of protein structure conservation. The "conserved" class includes Zic proteins from the Arthropoda, Mollusca, Annelida, Echinodermata, and Chordata (vertebrates and cephalochordates), whereas the "diverged" class contains those from the Platyhelminthes, Cnidaria, Nematoda, and Chordata (urochordates). The result indicates that the ancestral bilateralian Zic protein had already acquired an entire set of conserved domains, but that this was lost and diverged in the platyhelminthes, nematodes, and urochordates.

Amino Acid Sequence↗

PubMed2006

Xenopus Zic4: conservation and diversification of expression profiles and protein function among the Xenopus Zic family.

We compared the expression and function of Xenopus Zic4 with those of the other four Xenopus laevis Zic family members (Zic1, Zic2, Zic3, and Zic5). Zic4 expression was detected mainly in the neural plate border, dorsal neural tube, and somites, and was similar to that of Zic1, which is adjacent to Zic4 on the same chromosome. Injection of wild-type or mutant Zic4 RNA caused the induction of neural crest marker gene expression, hyperplastic neural tissue, and ectopic pigment cell formation, indicating that Zic4 can induce neural and neural crest tissue, as can other Xenopus Zic genes. Deletion analysis showed that the zinc-finger domain is critical for many Zic4 functions, but the C-terminal region is differently involved in induction of two neural crest markers, Slug and Sox10. The protein function as determined by the animal cap explant assay was similar to that of Zic5, but different from those of Zic1, Zic2, and Zic3, suggesting that Xenopus Zic genes can be divided into two groups based on function. These results indicate that the five Xenopus Zic genes cooperatively regulate both neural and neural crest development, despite significantly diverged expression profiles and functions.

Amino Acid Sequence↗

PubMed2005

IP3 receptor types 2 and 3 mediate exocrine secretion underlying energy metabolism.

Type 2 and type 3 inositol 1,4,5-trisphosphate receptors (IP3R2 and IP3R3) are intracellular calcium-release channels whose physiological roles are unknown. We show exocrine dysfunction in IP3R2 and IP3R3 double knock-out mice, which caused difficulties in nutrient digestion. Severely impaired calcium signaling in acinar cells of the salivary glands and the pancreas in the double mutants ascribed the secretion deficits to a lack of intracellular calcium release. Despite a normal caloric intake, the double mutants were hypoglycemic and lean. These results reveal IP3R2 and IP3R3 as key molecules in exocrine physiology underlying energy metabolism and animal growth.

Amylases↗

PubMed2004

Molecular properties of Zic4 and Zic5 proteins: functional diversity within Zic family.

The Zic-family proteins control various developmental processes. Previous studies have shown that Zic1, Zic2, and Zic3 can act as transcriptional regulators, and that their functions are repressed by I-mfa, which has been identified as a repressor for basic helix-loop-helix-type transcriptional factors. Here, we investigated the molecular properties of the Zic4 and Zic5 proteins. Zic4/Zic5 showed DNA-binding activity to the Gli-binding sequence, similar to Zic1/Zic2/Zic3 proteins. However, Zic4/Zic5 did not exhibit any significant transcriptional activation ability nor they bind to I-mfa differently from Zic1/Zic2/Zic3. The nuclear localization of Zic4/Zic5 was not affected by the presence of the I-mfa protein, whereas the Zic1/Zic2/Zic3 proteins were translocated to the cytoplasmic compartment in the presence of I-mfa. The difference may be attributable to the dissimilarity of the N-terminal region between the Zic1/Zic2/Zic3 and Zic4/Zic5 proteins, since the binding of the Zic1/Zic2/Zic3 proteins to I-mfa occurs through their N-terminal regions.

Amino Acid Sequence↗

PubMed2004

Myogenic repressor I-mfa interferes with the function of Zic family proteins.

Zinc finger proteins belonging to the Zic family control several developmental processes such as patterning of the axial skeleton. Here we mapped the transcriptional regulatory domains in Zic2 protein and identified a protein which specifically binds to one of them. In the mapping experiments, an amino-terminal region was identified as transcriptional regulatory domains. A search for proteins binding to the amino terminal domain of Zic2 revealed that inhibitor of MyoD family (I-mfa) protein, which has been identified as a repressor of myogenic helix-loop-helix class transcription factors, can physically interact with the amino terminal domain. When Zic1-3 and I-mfa proteins were co-expressed in cultured cells, nuclear import of the Zic proteins was inhibited. Consequently, I-mfa inhibited transcriptional activation by the Zic proteins in cultured cells. These results suggest that the physical and functional interaction between Zic and I-mfa proteins can play a role in the vertebrate development.

3T3 Cells↗

PubMed2004

Mouse Zic5 deficiency results in neural tube defects and hypoplasia of cephalic neural crest derivatives.

Zic family genes encode zinc finger proteins, which are homologues of the Drosophila pair-rule gene odd-paired. In the present study, we characterized the fifth member of the mouse Zic family gene, mouse Zic5. Zic5 is located near Zic2, which is responsible for human brain malformation syndrome (holoprosencephaly, or HPE). In embryonic stages, Zic5 was expressed in dorsal part of neural tissues and limbs. Expression of Zic5 overlapped with those of other Zic genes, most closely with Zic2, but was not identical. Targeted disruption of Zic5 resulted in insufficient neural tube closure at the rostral end, similar to that seen in Zic2 mutant mice. In addition, the Zic5-deficient mice exhibited malformation of neural-crest-derived facial bones, especially the mandible, which had not been observed in other Zic family mutants. During the embryonic stages, there were delays in the development of the first branchial arch and extension of the trigeminal and facial nerves. Neural crest marker staining revealed fewer neural crest cells in the dorsal cephalic region of the mutant embryos without significant changes in their migration. When mouse Zic5 was overexpressed in Xenopus embryos, expression of a neural crest marker was enhanced. These findings suggested that Zic5 is involved in the generation of neural crest tissue in mouse development. ZIC5 is also located close to ZIC2 in humans, and deletions of 13q32, where ZIC2 is located, lead to congenital brain and digit malformations known as the "13q32 deletion syndrome". Based on both their similar expression pattern in mouse embryos and the malformations observed in Zic5-deficient mutant mice, human ZIC5 might be involved in the deletion syndrome.

Animals↗

PubMed2004

The role of Zic genes in neural development.

The Zic family of zinc-finger proteins plays a crucial role in neural development. Zic genes are vertebrate homologs of odd-paired, the Drosophila pair-rule gene. Their gene products have zinc-finger domains similar to those of Gli proteins, which act as transcriptional regulators in hedgehog signaling. Recent studies of human, mouse, frog, fish and ascidian Zic homologs have provided evidence that Zic genes are involved in a variety of developmental processes, including neurogenesis, myogenesis, skeletal patterning, and left-right axis establishment. Zic genes appear to have multiple roles in neural development. They control the initial phase during which ectoderm differentiates into neuroectoderm, and they may act as bridges between secreted neural tissue induction signals and the basic-helix-loop-helix class of neurogenesis-inducing transcriptional regulatory factors. Studies of loss-of-function mutations with differing Zic gene subtypes show that the Zic family of genes controls the process of neurulation. Mutations result in neural tube defects, which are seen at different rostrocaudal levels depending on which Zic gene subtype has been affected. Development of holoprosencephaly, forebrain anomalies, and cerebellar dysgenesis indicate that region-specific morphogenesis of the CNS is also controlled by Zic genes. The underlying molecular actions of Zic gene products, which allow them to control development, remain a mystery. Recent molecular characterization has shown that Zic proteins are able to bind Gli-binding DNA sequences in a sequence-specific manner, but with lower affinity than Gli proteins. Zic proteins also can activate transcription from several promoters. Furthermore, Zic and Gli proteins interact physically via their zinc-finger domains, raising the possibility that Zic proteins can act as transcriptional cofactors and modulate the hedgehog-signaling pathway. Clarification of the specific cooperating factors is therefore required in each case. Other evidence also suggests that Zic proteins can inhibit neuronal differentiation by activating Notch signals. This association might be is a clue toward understanding of the multifunctional property of Zic proteins because Notch signaling also is implicated in the control of several developmental processes.

Animals↗

PubMed2004

Locomotor and oculomotor impairment associated with cerebellar dysgenesis in Zic3-deficient (Bent tail) mutant mice.

We examined the adult neural phenotypes of the Bent tail mutant mouse. The Bent tail mutant mouse was recently shown to lack a submicroscopic part of the X chromosome containing the Zic3 gene, which encodes a zinc-finger protein controlling vertebrate neural development. While nearly one-fourth of hemizygous Bent tail (Bn/Y, Zic3-deficient) mice developed neural tube defects in their midbrain and hindbrain region, the other Bn/Y mice showed apparently normal behaviour in a C57BL/6 genetic background. A battery of behavioural and eye movement tests revealed impaired spontaneous locomotor activity, reduction of muscle tone and impairments of vestibuloocular and optokinetic eye movements in these mice. Morphological examination of the mutant brain showed a significant reduction in the cell numbers in the cerebellar anterior lobe and paraflocculus-flocculus complex. Our results indicate that the cerebellar dysgenesis characterized by subregional hypoplasia affects the locomotor activity, muscle tone and eye movement control of the mice. These findings may have some clinical implications in relation to disorders characterized by cerebellar dysgenesis, such as Joubert syndrome.

Animals↗

PubMed2003

Dorz1, a novel gene expressed in differentiating cerebellar granule neurons, is down-regulated in Zic1-deficient mouse.

The Zic1 gene encodes a zinc finger protein that controls vertebrate neural development. A previous study showed that Zic1 is expressed in developing and mature cerebellar granule neurons, and that Zic1-deficient cerebellum is hypoplastic and lacks a lobule of the anterior lobe. In the present study, we searched for genes de-regulated in the cerebellum to understand the molecular basis of cerebellar development. A novel gene, Dorz1, was identified and characterized as one of the most significantly down-regulated genes in Zic1-deficient cerebellum by the DNA microarray analysis. The expression of Dorz1 in the developing cerebellum peaked at embryonic day 17.5, and at that stage Dorz1 transcripts were detected in cerebellar granule neuron precursors where Zic1 expression is enhanced. In addition, Dorz1 expression was up-regulated in cultured cells overexpressing Zic1. These results suggest that Dorz1 expression is positively regulated by Zic1 during cerebellar development.

Aging↗

PubMed2003

Human SLITRK family genes: genomic organization and expression profiling in normal brain and brain tumor tissue.

Slitrk family proteins are characterized as integral membrane proteins that have two leucine-rich repeat (LRR) domains and a carboxy-terminal domain that is partially similar to trk neurotrophin receptor proteins. The LRR domains are similar to those of slit proteins. In a previous study, we showed that mouse Slitrk genes are expressed predominantly in neural tissue and have neurite-modulating activity in cultured neuronal cells. Their expression profiles as well as their functions vary among the family members. In this paper, we characterized the human SLITRK1, SLITRK2, SLITRK3, SLITRK4, SLITRK5, and SLITRK6 genes. The six genes are located in three clusters, on 3q, 13q, and Xq, respectively. Their expression was detected mainly in the brain, but the expression profile of each SLITRK was unique. SLITRK expression was also investigated in various types of brain tumor tissue. The results showed that all SLITRK genes are differentially expressed in brain tumors, including astrocytoma, oligodendroglioma, glioblastoma, medulloblastoma, and supratentorial primitive neuroectodermal tumor (PNET). Particularly interesting findings were that SLITRK3 expression was enhanced in tissue from several different types of tumors and SLITRK6 expression was highly selective. These results suggest that the human SLITRK genes are useful molecular indicators of brain tumor properties.

Adolescent↗

PubMed2003

Zic2 patterns binocular vision by specifying the uncrossed retinal projection.

During CNS development, combinatorial expression of transcription factors controls neuronal subtype identity and subsequent axonal trajectory. Regulatory genes designating the routing of retinal ganglion cell (RGC) axons at the optic chiasm to the appropriate hemisphere, a pattern critical for proper binocular vision, have not been identified. Here, we show that the zinc finger transcription factor Zic2, a vertebrate homolog of the Drosophila gene odd-paired, is expressed in RGCs with an uncrossed trajectory during the period when this subpopulation grows from the ventrotemporal retina toward the optic chiasm. Loss- and gain-of-function analyses indicate that Zic2 is necessary and sufficient to regulate RGC axon repulsion by cues at the optic chiasm midline. Moreover, Zic2 expression reflects the extent of binocularity in different species, suggesting that Zic2 is an evolutionarily conserved determinant of RGCs that project ipsilaterally. These data provide evidence for transcriptional coding of axon pathfinding at the midline.

Animals↗

PubMed2003

Identification and characterization of Slitrk, a novel neuronal transmembrane protein family controlling neurite outgrowth.

The Slitrk family consists of six structurally related transmembrane proteins (Slitrk1-6) in the mouse. In the extracellular region, they share two conserved leucine-rich repeat domains that have a significant homology to a secreted axonal growth-controlling protein, Slit. These proteins also have a homology to trk neurotrophin receptors in their intracellular domains, sharing a conserved tyrosine residue. Expression of Slitrk is highly restricted to neural tissues, but varies within the family. More specifically, Slitrk1 expression is in the mature neurons, whereas Slitrk2 is strongly expressed in the ventricular layer, and Slitrk6 shows compartmentalized expression in diencephalon. Over-expressed Slitrk1 induced unipolar neurites in cultured neuronal cells, whereas Slitrk2 and other Slitrk proteins inhibited neurite outgrowth. Deletion analysis showed that the functional difference between Slitrk1 and Slitrk2 lies in their intracellular domains, which are conserved in Slitrk2-6, but not in Slitrk1. These results suggest that the Slitrk proteins are the neuronal components that control the neurite outgrowth.

Amino Acid Sequence↗

PubMed2003

Slitrk6 expression profile in the mouse embryo and its relationship to that of Nlrr3.

Slitrk6 is a member of the Slitrk family of proteins, which are integral membrane proteins possessing two leucine-rich repeat (LRR) domains and a carboxy-terminal domain partially similar to that in the trk neurotrophin receptor proteins. Here, I show that Slitrk6 is uniquely expressed in various organs, different from other Slitrk genes which are predominantly expressed in neural tissues. In the developing mouse embryo, Slitrk6 expression was detected in the otic cyst, lateral trunk epidermis and its underlying mesenchymal tissue, limb bud, maxillary process, pharyngeal arches, cochlea, retina, tongue, tooth primordium, central nervous system (CNS), and the visceral organ primordia including of the lung, gastrointestinal tract (particularly in the enteric neurons) and pancreas. The expression in these organs occurred in a spatially restricted manner. In the CNS, the expression was highly compartmentalized in the dorsal thalamus, cerebellum and medulla. The expression compartment in the thalamus in which Slitrk6 was expressed was closely related to the Gbx2-expressing prosomere 2. Interestingly, the Slitrk6 expression in the CNS, cochlea, tongue, tooth primordial, and other organs was partially complementary to the expression of Nlrr3, which belongs to another family of neuronal LRR-containing transmembrane proteins. The complementary expression of the two proteins in the dorsal thalamus persisted from E13.5 to the adult stage.

Animals↗

PubMed2002

Zic1 promotes the expansion of dorsal neural progenitors in spinal cord by inhibiting neuronal differentiation.

The role of Zic1 was investigated by altering its expression status in developing spinal cords. Zic genes encode zinc finger proteins homologous to Drosophila Odd-paired. In vertebrate neural development, they are generally expressed in the dorsal neural tube. Chick Zic1 was initially expressed evenly along the dorsoventral axis and its expression became increasingly restricted dorsally during the course of neurulation. The dorsal expression of Zic1 was regulated by Sonic hedgehog, BMP4, and BMP7, as revealed by their overexpressions in the spinal cord. When Zic1 was misexpressed on the ventral side of the chick spinal cord, neuronal differentiation was inhibited irrespective of the dorsoventral position. In addition, dorsoventral properties were not grossly affected as revealed by molecular markers. Concordantly, when Zic1 was overexpressed in the dorsal spinal cord in transgenic mice, we observed hypercellularity in the dorsal spinal cord. The transgene-expressing cells were increased in comparison to those of truncated mutant Zic1-bearing mice. Conversely, we observed a significant cell number reduction without loss of dorsal properties in the dorsal spinal cords of Zic1-deficient mice. Taken together, these findings suggest that Zic1 controls the expansion of neuronal precursors by inhibiting the progression of neuronal differentiation. Notch-mediated inhibition of neuronal differentiation is likely to act downstream of Zic genes since Notch1 is upregulated in Zic1-overexpressing spinal cords in both the mouse and the chick.

Animals↗

PubMed2002

Zic2 controls cerebellar development in cooperation with Zic1.

Mouse Zic genes encode zinc finger proteins and are expressed in the developing and mature CNS. Reduced expression of Zic2 in mice results in spina bifida and holoprosencephaly. However, the disruption of Zic1, a strong homolog of Zic2 that has an overlapping expression pattern, results in cerebellar malformation with no apparent abnormalities in the forebrain or in posterior neuropore closure. Here we revealed that Zic2 and Zic1 cooperatively control cerebellar development by regulating neuronal differentiation. Both Zic1 and Zic2 are expressed in the precursor cells of the granule neuron and the neurons in cerebellar nuclei. Mice carrying one mutated Zic1 allele together with one mutated Zic2 allele (Zic1(+/-)Zic2(+/kd)) showed a marked cerebellar folial abnormality similar to, but distinct from that found in mice homozygous for the Zic1 mutation (Zic1(-/-)). The Zic1(+/-)Zic2(+/kd) cerebellum is missing a lobule in the anterior vermis and has a truncation of the most posterior lobule. Expression of transverse zonal markers is shifted anteriorly in the developing cerebellum, indicating that the anterior part of the cerebellum is poorly developed. Abnormalities in the developing Zic1(+/-)Zic2(+/kd) cerebellum share the following features with those of the Zic1(-/-) cerebellum: a preceding reduction of cell proliferation in the anterior external germinal layer, a reduction in cyclin D1 expression, and enhanced expression of the mitosis inhibitors p27 and p16, and enhancement of Wnt7a expression. These results indicate that Zic1 and Zic2 may have very similar functions in the regulation of cerebellar development.

Animals↗

PubMed2002

Xenopus Brachyury regulates mesodermal expression of Zic3, a gene controlling left-right asymmetry.

The Brachyury gene has a critical role in the formation of posterior mesoderm and notochord in vertebrate development. A recent study showed that Brachyury is also responsible for the formation of the left-right (L-R) axis in mouse and zebrafish. However, the role of Brachyury in L-R axis specification is still elusive. Here, it is demonstrated that Brachyury is involved in L-R specification of the Xenopus laevis embryo and regulates expression of Zic3, which controls the L-R specification process. Overexpression of Xenopus Brachyury (Xbra) and dominant-negative type Xbra (Xbra-EnR) altered the orientation of heart and gut looping, concomitant with disturbed laterality of nodal-related 1 (Xnr1) and Pitx2 expression, both of which are normally expressed in the left lateral plate mesoderm. Furthermore, activation of inducible type Xbra (Xbra-GR) induces Zic3 expression within 20 min. These results suggest that a role of Brachyury in L-R specification may be the direct regulation of Zic3 expression.

Animals↗