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DNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 5; DNAJC5

DNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 5; DNAJC5

Alternative titles; symbolsDNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 5, ALPHA; DNAJC5ACYSTEINE STRING PROTEIN; CSPCSP-ALPHAHGNC Approved Gene Symbol: DNAJC5Cytogen...

Alternative titles; symbols

  • DNAJ/HSP40 HOMOLOG, SUBFAMILY C, MEMBER 5, ALPHA; DNAJC5A
  • CYSTEINE STRING PROTEIN; CSP
  • CSP-ALPHA

HGNC Approved Gene Symbol: DNAJC5

Cytogenetic location: 20q13.33 Genomic coordinates (GRCh38): 20:63,895,125-63,936,025 (from NCBI)

▼ Description
The DNAJC5 gene encodes the cysteine string protein, a presynaptic J protein expressed in neural tissues as well as in synaptic and clathrin-coated vesicles (summary by Cadieux-Dion et al., 2013).

▼ Cloning and Expression
Using antibody directed against rat Csp to screen a brain cDNA expression library, Coppola and Gundersen (1996) obtained a full-length human CSP clone. The deduced 198-amino acid protein differs from rat Csp at only 1 residue. Coppola and Gundersen (1996) also cloned a splice variant of CSP that contains a 72-nucleotide insertion that introduces an in-frame stop codon. This variant encodes a deduced 167-amino acid protein that is identical to the full-length protein for the first 164 amino acids. Northern blot analysis detected at least 3 CSP variants in all 8 human tissues examined. Western blot analysis of human blood detected CSP at an apparent molecular mass of 35 kD. Treatment with a deacylating agent caused a downward shift of 7 kD in apparent mass.

Tobaben et al. (2001) showed that the 198-amino acid rat Csp protein contains an N-terminal J domain, followed by a cysteine string and a C-terminal domain. They noted that most of the cysteines are palmitoylated and are required for membrane targeting of Csp.

Using real-time RT-PCR, Fernandez-Chacon et al. (2004) detected Csp-alpha in mouse brain and testis.

Natochin et al. (2005) stated that rat Csp has 2 binding sites for G proteins, one that overlaps the J domain and binds G-alpha subunits (see GNAS, 139320), and another between the J domain and cysteine string that binds G-beta (see GNB1, 139380) and/or the G-alpha-beta-gamma (see GNG2, 606981) trimer.

▼ Gene Function
Tobaben et al. (2001) showed that rat Csp interacted with Sgt (SGTA; 603419) and Hsc70 (HSPA8; 600816) in a complex located on the synaptic vesicle surface. The complex functioned as an ATP-dependent chaperone that reactivated a denatured substrate. Sgt overexpression in cultured rat hippocampal neurons inhibited neurotransmitter release, suggesting that the Csp/Sgt/Hsc70 complex is important for maintenance of a normal synapse.

Miller et al. (2003) stated that rat Csp binds both the N-type calcium channel (see 601012) and G protein beta-gamma subunits in vitro, and that these associations give rise to tonic G protein inhibition of the calcium channel. They showed that an N-terminal fragment of human huntingtin (HTT; 613004) with an expanded polyglutamine tract blocked association of Csp with G proteins and eliminated Csp's tonic G protein inhibition of N-type calcium channels. In contrast, an N-terminal huntingtin fragment without an expanded polyglutamine tract did not alter association of Csp with G proteins and had no effect on channel inhibition by Csp.

Natochin et al. (2005) showed that rat Csp stimulated GDP/GTP exchange on G-alpha-S. Modulation of G proteins by Csp was, in turn, regulated by Hsc70 and Sgt.

▼ Mapping
Gross (2011) mapped the DNAJC5 gene to chromosome 20q13.33 based on an alignment of the DNAJC5 sequence (GenBank BC053642) with the genomic sequence (GRCh37).

▼ Molecular Genetics
In a Czech family with an autosomal dominant form of Kufs disease, ceroid neuronal lipofuscinosis-4 (CLN4; 162350), Noskova et al. (2011) identified a heterozygous 3-bp deletion in the DNAJC5 gene (346_348delCTC; 611203.0001), resulting in deletion of leu116. The mutation was found by a combination of linkage analysis, copy-number analysis, gene-expression analysis, and exome sequencing of candidate genes. Screening of this gene in 20 additional families identified pathogenic mutations, including a novel missense mutation (L115R; 611203.0002), in 4. Two of the families had been reported by Josephson et al. (2001) and Nijssen et al. (2002). The patients had onset of rapidly progressive neurodegenerative disorder with onset in the third or fourth decades.

In patients with CLN4, Benitez et al. (2011) and Velinov et al. (2012) found the same 2 heterozygous mutations in the DNAJC5 gene as those reported by Noskova et al. (2011), thus confirming the findings. Benitez et al. (2011) studied the family originally reported by Josephson et al. (2001), and Velinov et al. (2012) studied the Parry family originally reported by Boehme et al. (1971).

By linkage analysis combined with exome sequencing in the large family (Parry family) with adult-onset CLN reported by Boehme et al. (1971), Cadieux-Dion et al. (2013) also identified heterozygosity for the same 3-bp deletion mutation in the DNAJC5 gene (611203.0001). The mutation was confirmed by Sanger sequencing, was not found in 380 control chromosomes, and segregated with the disorder in the family. The American patient reported by Noskova et al. (2011) who carried this mutation was found to be from the Parry family. Cadieux-Dion et al. (2013) also identified the leu116del mutation in affected members of a family from Alabama reported by Burneo et al. (2003). Haplotype analysis did not show a founder effect between the 2 families, suggesting that it is a recurrent mutation. Cadieux-Dion et al. (2013) also identified a heterozygous L115R mutation in the DNAJC5 gene (611203.0002) in 1 of 6 additional patients with the disorder; this patient had no family history. Overall, DNAJC5 mutations accounted for 38% of cases with unexplained adult-onset NCL in their cohort, with the mutations occurring at mutational hotspots.

▼ Animal Model
Fernandez-Chacon et al. (2004) found that Csp-alpha -/- mice appeared normal at birth but developed a progressive lethal phenotype that manifested as muscle weakness and a sensorimotor disorder at 2 to 4 weeks of age. Analysis of synaptic transmission in Csp-alpha -/- neuromuscular junctions and at the Calyx of Held synapse revealed normal Ca(2+) channel function and Ca(2+)-dependent exocytosis. However, synapses showed progressively worsening presynaptic degeneration, with persistent vacuoles, proliferation of multilamellar bodies, and protrusion of Schwann cell fingers into the neuromuscular nerve terminal. Coppola and Gundersen (1996) concluded that the degeneration of Csp-alpha -/- synapses appeared to occur in a use-dependent manner and that CSP-alpha is required to maintain the integrity of synapses in the face of use-dependent stress.

▼ ALLELIC VARIANTS ( 2 Selected Examples):

.0001 CEROID LIPOFUSCINOSIS, NEURONAL, 4 (KUFS TYPE)
DNAJC5, 3-BP DEL, 346CTC
In affected members of a Czech family with an autosomal dominant form of Kufs disease, neuronal ceroid lipofuscinosis-4 (CLN4; 162350), Noskova et al. (2011) identified a heterozygous 3-bp deletion (346_348delCTC) in the DNAJC5 gene, resulting in a deletion of leu116 (Leu116del) in a conserved region of the cysteine-string domain of the protein. Screening of this gene in 20 additional families identified this mutation in 1 affected American patient who had a family history of the disorder. The patients had onset of rapidly progressive neurodegenerative disorder with onset in the third or fourth decades. Haplotype analysis did not suggest a common origin. The mutation was not found in 200 controls. In vitro functional expression in CAD5 neuronal cells showed that the mutant protein had abnormal diffuse intracellular localization and abnormal colocalization with markers for the endoplasmic reticulum and Golgi apparatus. Immunoblot analysis indicated that the mutant protein was less efficiently palmitoylated compared to wildtype. Analysis of brain tissue from affected individuals showed significantly reduced immunostaining for DNAJC5 in the cerebral cortex compared to controls.

Benitez et al. (2011) identified the heterozygous 346_348delCTC mutation in affected members of a family with CLN4. The mutation, which was found by Sanger sequencing, was not present in the dbSNP (build 134) or 1000 Genomes Project databases or in more than 3,200 control chromosomes. These findings confirmed the report of Noskova et al. (2011). Molecular modeling studies predicted that the mutation may weaken membrane binding by decreasing affinity of the protein for the membrane. Other functional studies were not performed.

Velinov et al. (2012) identified the 3-bp deletion mutation in affected members of the original Parry family with CLN4 (Boehme et al., 1971). Affected individuals also carried a heterozygous 1430A-G transition in the PRPF6 gene (613979), resulting in an asn477-to-ser (N477S) substitution at a highly conserved residue. The mutations, which were found by exome sequencing and confirmed by Sanger sequencing, segregated with the disorder in the family. Neither mutation was found in 2,100 control individuals. Both changes occurred within about 75 kb on chromosome 20 and were likely linked on a rare haplotype. Velinov et al. (2012) noted that a PRPF6 mutation has been associated with retinitis pigmentosa-60 (RP60; 613983) and that some members of the Parry family had unspecified visual problems, suggesting that it may be a phenotypic modifier in this family.

By linkage analysis combined with exome sequencing in the large family (Parry family) with adult-onset CLN reported by Boehme et al. (1971), Cadieux-Dion et al. (2013) identified a heterozygous 346_348del mutation. The mutation was confirmed by Sanger sequencing, was not found in 380 control chromosomes, and segregated with the disorder in the family. The American patient reported by Noskova et al. (2011) who carried this mutation was found to be from the Parry family. Cadieux-Dion et al. (2013) also identified the leu116del mutation in affected members of a family from Alabama reported by Burneo et al. (2003), even though the mutation in this family had not been found by Noskova et al. (2011). Haplotype analysis did not show a founder effect between the 2 families, suggesting that it is a recurrent mutation.

.0002 CEROID LIPOFUSCINOSIS, NEURONAL, 4 (KUFS TYPE)
DNAJC5, LEU115ARG
In affected members of 2 unrelated families and 1 patient with autosomal dominant Kufs disease (CLN4; 162350), Noskova et al. (2011) identified a heterozygous 344T-G transversion in the DNAJC5 gene, resulting in a leu115-to-arg (L115R) substitution in a conserved residue in the cysteine-string domain of the protein. Two of the families had been reported by Josephson et al. (2001) and Nijssen et al. (2002). The mutation was not found in 200 controls. Haplotype analysis did not suggest a common origin. In vitro functional expression in CAD5 neuronal cells showed that the mutant protein had abnormal diffuse intracellular localization and abnormal colocalization with markers for the endoplasmic reticulum and Golgi apparatus. Immunoblot analysis indicated that the mutant protein was less efficiently palmitoylated compared to wildtype. Analysis of brain tissue from affected individuals showed absence of immunostaining for DNAJC5 in synaptic regions in both the cerebral and cerebellar cortex compared to controls. However, there was some evidence for an insoluble DNAJC5-containing aggregate in brain lysate.

Benitez et al. (2011) identified a heterozygous L115R mutation in affected members of a large family with CLN4 originally reported by Josephson et al. (2001). The mutation, which was found by whole-exome sequencing and filtered against the dbSNP (build 130) and 1000 Genomes Project databases as well as 59 in-house exomes, was confirmed by Sanger sequencing to segregate with the disorder in the family. It was also absent in an additional 1,600 controls. Molecular modeling studies predicted that the mutation may weaken membrane binding by decreasing affinity of the protein for the membrane. Other functional studies were not performed. These findings confirmed the report of Noskova et al. (2011).

Velinov et al. (2012) identified a heterozygous L115R mutation in a patient with CLN4B.

Cadieux-Dion et al. (2013) identified a heterozygous L115R mutation in a patient with sporadic occurrence of CLN4B.

Tags: 20q13.33