Hydrolethalus syndrome is caused by missense mutation in a novel gene HYLS1

University of Helsinki, Helsinki, Uusimaa, Finland
Human Molecular Genetics (Impact Factor: 6.39). 07/2005; 14(11):1475-88. DOI: 10.1093/hmg/ddi157
Source: PubMed


Hydrolethalus syndrome (HLS) is an autosomal recessive lethal malformation syndrome characterized by multiple developmental defects of fetus. We have earlier mapped and restricted the HLS region to a critical 1 cM interval on 11q23-25. The linkage disequilibrium (LD) and haplotype analyses of single nucleotide polymorphism (SNP) markers helped to further restrict the HLS locus to 476 kb between genes PKNOX2 and DDX25. An HLS associated mutation was identified in a novel regional transcript (GenBank accession no. FLJ32915), referred to here as the HYLS1 gene. The identified A to G transition results in a D211G change in the 299 amino acid polypeptide with unknown function. The HYLS1 gene shows alternative splicing and the transcript is found in multiple tissues during fetal development. In situ hybridization shows spatial and temporal distributions of transcripts in good agreement with the tissue phenotype of HLS patients. Immunostaining of in vitro expressed polypeptides from wild-type (WT) cDNA revealed cytoplasmic staining, whereas mutant polypeptides became localized in distinct nuclear structures, implying a disturbed cellular localization of the mutant protein. The Drosophila melanogaster model confirmed these findings and provides evidence for the significance of the mutation both in vitro and in vivo.

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    • "Notably, HYLS-1-like proteins were not found in organisms that lack centrioles, such as fungi and higher plants. Hydrolethalus syndrome in humans is caused by a missense mutation that changes an invariant aspartic acid residue in the HYLS-1 box to glycine (Fig. 1D; Mee et al. 2005). With the exception of a common contaminant (HSP-1) no other proteins were copurified in the SAS-4 and HYLS-1 "
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    ABSTRACT: Centrioles are subcellular organelles composed of a ninefold symmetric microtubule array that perform two important functions: (1) They build centrosomes that organize the microtubule cytoskeleton, and (2) they template cilia, microtubule-based projections with sensory and motile functions. We identified HYLS-1, a widely conserved protein, based on its direct interaction with the core centriolar protein SAS-4. HYLS-1 localization to centrioles requires SAS-4 and, like SAS-4, HYLS-1 is stably incorporated into the outer centriole wall. Unlike SAS-4, HYLS-1 is dispensable for centriole assembly and centrosome function in cell division. Instead, HYLS-1 plays an essential role in cilia formation that is conserved between Caenorhabditis elegans and vertebrates. A single amino acid change in human HYLS1 leads to a perinatal lethal disorder termed hydrolethalus syndrome, and we show that this mutation impairs HYLS-1 function in ciliogenesis. HYLS-1 is required for the apical targeting/anchoring of centrioles at the plasma membrane but not for the intraflagellar transport-dependent extension of the ciliary axoneme. These findings classify hydrolethalus syndrome as a severe human ciliopathy and shed light on the dual functionality of centrioles, defining the first stably incorporated centriolar protein that is not required for centriole assembly but instead confers on centrioles the capacity to initiate ciliogenesis.
    Full-text · Article · Sep 2009 · Genes & development
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    • "When the cellular localization of the HYLS1 protein was studied in an overexpression cell model we detected the partially different localization of wild-type (wt) and mutant forms of the protein. While the wt form localizes mainly into the cytoplasm, the mutated form partly accumulates in the nucleus forming dot-like structures [5]. The function of the HYLS1 protein is not known and it lacks any known functional domains except a low-complexity region. "
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    ABSTRACT: Hydrolethalus syndrome (HLS) is a severe fetal malformation syndrome characterized by multiple developmental anomalies, including central nervous system (CNS) malformation such as hydrocephaly and absent midline structures of the brain, micrognathia, defective lobation of the lungs and polydactyly. Microscopically, immature cerebral cortex, abnormalities in radial glial cells and hypothalamic hamartoma are among key findings in the CNS of HLS fetuses. HLS is caused by a substitution of aspartic acid by glycine in the HYLS1 protein, whose function was previously unknown. To provide insight into the disease mechanism(s) of this lethal disorder we have studied different aspects of HLS and HYLS1. A genome-wide gene expression analysis indicated several upregulated genes in cell cycle regulatory cascades and in specific signal transduction pathways while many downregulated genes were associated with lipid metabolism. These changes were supported by findings in functional cell biology studies, which revealed an increased cell cycle rate and a decreased amount of apoptosis in HLS neuronal progenitor cells. Also, changes in lipid metabolism gene expression were reflected by a significant increase in the cholesterol levels of HLS liver tissues. In addition, based on our functional studies of HYLS1, we propose that HYLS1 is a transcriptional regulator that shuffles between the cytoplasm and the nucleus, and that when HYLS1 is mutated its function is significantly altered. In this study, we have shown that the HYLS1 mutation has significant consequences in the cellular and tissue levels in HLS fetuses. Based on these results, it can be suggested that HYLS1 is part of the cellular transcriptional regulatory machinery and that the genetic defect has a widespread effect during embryonic and fetal development. These findings add a significant amount of new information to the pathogenesis of HLS and strongly suggest an essential role for HYLS1 in normal fetal development.
    Full-text · Article · May 2009 · PathoGenetics
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    • "Hydrolethalus syndrome (HLS) most closely correlates with the gasping phenotype. As a relatively rare disorder affecting primarily Finnish families (Mee et al., 2005), little is known about the protein's function. The mouse homologue (Hyls1) maps to chromosome 9, within the gpg3 minimal region; while, therefore , a candidate, further mapping will be performed before this is tested. "
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    ABSTRACT: Vertebrate organs show consistent left-right (L-R) asymmetry in placement and patterning. To identify genes involved in this process we performed an ENU-based genetic screen. Of 135 lines analyzed 11 showed clear single gene defects affecting L-R patterning, including 3 new alleles of known L-R genes and mutants in novel L-R loci. We identified six lines (termed "gasping") that, in addition to abnormal L-R patterning and associated cardiovascular defects, had complex phenotypes including pulmonary agenesis, exencephaly, polydactyly, ocular and craniofacial malformations. These complex abnormalities are present in certain human disease syndromes (e.g., HYLS, SRPS, VACTERL). Gasping embryos also show defects in ciliogenesis, suggesting a role for cilia in these human congenital malformation syndromes. Our results indicate that genes controlling ciliogenesis and left-right asymmetry have, in addition to their known roles in cardiac patterning, major and unexpected roles in pulmonary, craniofacial, ocular and limb development with implications for human congenital malformation syndromes.
    Full-text · Article · Mar 2009 · Developmental Dynamics
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