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FOUR-JOINTED BOX, DROSOPHILA, HOMOLOG OF, 1; FJX1

FOUR-JOINTED BOX, DROSOPHILA, HOMOLOG OF, 1; FJX1

HGNC Approved Gene Symbol: FJX1Cytogenetic location: 11p13 Genomic coordinates (GRCh38): 11:35,618,459-35,620,864 (from NCBI)▼ Cloning and ExpressionThate et...

HGNC Approved Gene Symbol: FJX1

Cytogenetic location: 11p13 Genomic coordinates (GRCh38): 11:35,618,459-35,620,864 (from NCBI)

▼ Cloning and Expression
Thate et al. (1995) identified a novel human EST clone (NE3) by CpG island analyses on chromosome 11p13. By Northern blot analysis of 6 human tissues, Gawin et al. (1999) detected brain-specific expression of a 2.6-kb NE3 transcript, which they called 3K.

Ashery-Padan et al. (1999) identified the NE3 clone as the homolog of the Drosophila four-jointed gene (fj), which encodes a protein important for growth and differentiation of legs and wings and for proper development of the eyes. They cloned mouse Fjx1 from an embryonic day 8.5 cDNA library. Northern blot analysis identified a 2.8-kb Fjx1 transcript throughout development beginning at E11 and in adult brain. A weaker 1.7-kb transcript was detected at E7, but not during later stages of development. During mouse embryonic development, Fjx1 was expressed in the midbrain tectum and in telencephalic vesicles. In fetal and early postnatal brain, Fjx1 was expressed mainly in the primordia of layered telencephalic structures and in the superior colliculus. It was also expressed in the apical ectodermal ridge of fore- and hindlimbs and in the ectoderm of the branchial arches. In the adult, Fjx1 was expressed in neurons of the telencephalon, in the Purkinje layer of the cerebellum, and in numerous medullary nuclei. By Northern blot analysis, Gawin et al. (1999) detected high expression of mouse Fjx1 in brain and weak expression in kidney.

▼ Gene Structure
Ashery-Padan et al. (1999) stated that FJX1 is an intronless gene.

▼ Gene Function
The atypical cadherin Fat (600976) acts as a receptor for a signaling pathway that regulates growth, gene expression, and planar cell polarity. Genetic studies in Drosophila identified the four-jointed gene as a regulator of Fat signaling. Ishikawa et al. (2008) showed that four-jointed encodes a protein kinase that phosphorylates serine or threonine residues within extracellular cadherin domains of Fat and its transmembrane ligand, Dachsous (see 603057). Four-jointed functions in the Golgi and was the first molecularly defined kinase that phosphorylates protein domains destined to be extracellular. An acidic sequence motif (Asp-Asn-Glu) within four-jointed was essential for its kinase activity in vitro and for its biologic activity in vivo. Ishikawa et al. (2008) concluded that four-jointed regulates Fat signaling by phosphorylating cadherin domains of Fat and Dachsous as they transit through the Golgi.

▼ Mapping
Thate et al. (1995) mapped the FJX1 gene to chromosome 11p13 by CpG island analyses.

Tags: 11p13