| *300157 | |||||||||||||||||||||||||||||||||
| ACYL-CoA SYNTHETASE LONG CHAIN FAMILY, MEMBER 4; ACSL4 | |||||||||||||||||||||||||||||||||
| Alternative titles; symbols | |||||||||||||||||||||||||||||||||
| FATTY ACID CoA LIGASE, LONG CHAIN 4; FACL4 ACYL-CoA SYNTHETASE 4; ACS4 | |||||||||||||||||||||||||||||||||
| HGNC Approved Gene Symbol: ACSL4 | |||||||||||||||||||||||||||||||||
| Cytogenetic location: Xq23 Genomic coordinates (GRCh37): X:108,884,563 - 108,976,620 (from NCBI) | |||||||||||||||||||||||||||||||||
| Gene Phenotype Relationships | |||||||||||||||||||||||||||||||||
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| TEXT | |||||||||||||||||||||||||||||||||
| Description | |||||||||||||||||||||||||||||||||
| Long chain acyl-CoA synthetase (LACS), or long chain fatty acid-CoA ligase (FACL; EC 6.2.1.3), converts free long chain fatty acids into fatty acyl-CoA esters, which are key intermediates in the synthesis of complex lipids. The ACSL4 gene encodes a form of LACS and is expressed in several tissues, including brain (Cao et al., 1998; Piccini et al., 1998). | |||||||||||||||||||||||||||||||||
| Cloning | |||||||||||||||||||||||||||||||||
| Kang et al. (1997) identified rat Acsl4, which they called Acs4. By searching databases with rat Acs4 as query, Cao et al. (1998) identified ESTs encoding human ACSL4, which they called FACL4. They used the ESTs to identify a brain cDNA containing the remainder of the FACL4 coding region. The predicted 670-amino acid human protein is 97% identical to rat Acs4. Independently, Piccini et al. (1998) cloned FACL4 cDNAs. Northern blot analysis revealed that FACL4 was expressed as a 5-kb mRNA in a variety of tissues. The transcript in brain appeared to be slightly larger. Sequence analysis of FACL4 cDNAs showed that the larger mRNAs result from alternative splicing and encode a predicted protein with 41 additional N-terminal amino acids. The authors stated that the 41-amino acid peptide is hydrophobic and suggested that it may change the intracellular localization of FACL4 or its fatty acid specificity. Meloni et al. (2002) found that FACL4 was highly expressed in adult human brain, especially in cerebellum and hippocampus, and showed a distribution similar to that obtained in mouse. A strong cytoplasmic staining was found in Purkinje and granular cells of cerebellum and in the pyramidal layer of hippocampus, indicating that FACL4 is specifically expressed in neurons and not in glial cells. Within the neuron, FACL4 was found primarily in neuronal soma and proximal dendrites. Vitelli et al. (2000) cloned the mouse Facl4 gene. | |||||||||||||||||||||||||||||||||
| Gene Structure | |||||||||||||||||||||||||||||||||
| Minekura et al. (2001) determined that the ACSL4 gene contains 16 exons and spans approximately 90 kb. The 5-prime flanking region does not have a typical TATA box, but it has a CCAAT box and transcription factor-binding sites for AP2 (see 107580), AP4 (600743), and CREB (123810). Minekura et al. (2001) identified several other potential binding sites. Watkins et al. (2007) determined that the ACSL4 gene contains at least 17 exons. | |||||||||||||||||||||||||||||||||
| Mapping | |||||||||||||||||||||||||||||||||
| By somatic cell hybrid analysis and FISH, Cao et al. (1998) mapped the ACSL4 gene to chromosome Xq23. Piccini et al. (1998) further refined the map position to chromosome Xq22.3 by showing that the ACSL4 gene was contained within a YAC contig from that region. Watkins et al. (2007) mapped the ACSL4 gene to the minus strand of chromosome Xq22.3-q23 by genomic sequence analysis. Vitelli et al. (2000) mapped the mouse Acsl4 gene to chromosome XF1-F3 by FISH. | |||||||||||||||||||||||||||||||||
| Gene Function | |||||||||||||||||||||||||||||||||
| Kang et al. (1997) showed that rat Acs4 preferentially used arachidonate and eicosapentaenoate as substrates. Cao et al. (1998) showed that human FACL4 exhibited FACL activity with a preference for arachidonic acid as substrate when expressed in mammalian cells. | |||||||||||||||||||||||||||||||||
| Molecular Genetics | |||||||||||||||||||||||||||||||||
| Piccini et al. (1998) reported that the 2 patients with Alport syndrome, elliptocytosis, and mental retardation described by Jonsson et al. (1998) (300194) carried a large deletion of the COL4A5 (303630) region that included the contiguous FACL4. Piccini et al. (1998) suggested that the absence of FACL4 might play a role in the development of mental retardation or other signs associated with Alport syndrome in these patients. Meloni et al. (2002) reported the identification of 2 point mutations, 1 missense and 1 splice site change, in the FACL4 gene in 2 families with nonspecific mental retardation (MRX63; 300387). Analysis of enzymatic activity in lymphoblastoid cell lines of affected individuals of both families revealed low levels compared with normal cells, indicating that both mutations are null mutations. All carrier females with either point mutations or genomic deletions in FACL4 showed a completely skewed X inactivation, suggesting that the gene influences survival advantage. | |||||||||||||||||||||||||||||||||
| Animal Model | |||||||||||||||||||||||||||||||||
| Cho et al. (2001) found that female mice heterozygous for Facl4 deficiency became pregnant less frequently and produced small litters, with 40% of embryos surviving gestation. The transmission rate for the disrupted allele was low. Heterozygous females had extremely enlarged uteri and lumina filled with numerous proliferative cysts, and showed marked uterine accumulation of prostaglandins. Hemizygous males (-/Y) appeared normal and were fertile when crossed with wildtype females. Zhang et al. (2009) demonstrated that the Drosophila ACSL-like protein, Acsl, and ACSL4 are highly conserved, allowing ACSL4 to substitute for Acsl in organismal viability, lipid storage, and the neural wiring in the visual center. In neurodevelopment, production of decapentaplegic (Dpp), a BMP-like protein in Drosophila, diminished specifically in the larval brain of Drosophila Acsl mutants. Consistent with the Dpp reduction, the number of glial cells and neurons dramatically decreased and the retinal axons mistargeted in the visual cortex. All of these defects in Drosophila brain were rescued by the wildtype ACSL4 but not by the mutant products found in nonsyndromic X-linked mental retardation patients. Expression of an MRX63-associated ACSL4 mutant form in a wildtype background led to lesions in the visual center, suggesting a dominant-negative effect. Zhang et al. (2009) proposed a connection between ACSL4 and the BMP pathway in neurodevelopment. | |||||||||||||||||||||||||||||||||
| ALLELIC VARIANTS (Selected Examples): | |||||||||||||||||||||||||||||||||
| Table View | |||||||||||||||||||||||||||||||||
| .0001 MENTAL RETARDATION, X-LINKED 63 | |||||||||||||||||||||||||||||||||
| ACSL4, ARG529SER | |||||||||||||||||||||||||||||||||
| In a family segregating nonsyndromic X-linked mental retardation (MRX63; 300387), Meloni et al. (2002) identified a C-to-A transversion at nucleotide 1585 in exon 15 of the FACL4 gene, leading to an arg-to-ser substitution in amino acid 529 (R529S), corresponding to amino acid 570 of the brain isoform (R570S). All females carrying this mutation had completely skewed X inactivation in leukocytes. | |||||||||||||||||||||||||||||||||
| .0002 MENTAL RETARDATION, X-LINKED 63 | |||||||||||||||||||||||||||||||||
| ACSL4, IVS10, A-G, -2 | |||||||||||||||||||||||||||||||||
| In a patient with severe nonspecific X-linked mental retardation (MRX63; 300387), Meloni et al. (2002) identified an A-to-G transition at the -2 position of the splice site of intron 10 of the FACL4 gene (1003-2A-G), resulting in activation of a cryptic splice site within the intron and inducing an additional 28 nucleotides with an in-frame stop codon. This mutation was not identified in 600 normal control chromosomes. The carrier mother of the affected male had completely skewed X inactivation in leukocytes. | |||||||||||||||||||||||||||||||||
| .0003 MENTAL RETARDATION, X-LINKED 68 | |||||||||||||||||||||||||||||||||
| ACSL4, PRO375LEU | |||||||||||||||||||||||||||||||||
| In affected members of a family with nonspecific X-linked mental retardation (MRX68; 300387), Longo et al. (2003) identified a 1001C-T change in the FACL4 gene, resulting in a pro375-to-leu (P375L) substitution. Carrier females had 100% skewed X inactivation. Functional studies of the mutant protein showed a marked reduction in enzyme activity. The authors suggested that reduction of FACL4 activity may lead to deranged fatty acid metabolism in neurons, causing defects of neuron outgrowth, synaptogenesis, and other developmental functions important for normal brain development. | |||||||||||||||||||||||||||||||||
| REFERENCES | |||||||||||||||||||||||||||||||||
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