Evidence of a genetic background predisposing to complex regional pain syndrome type 1.

BACKGROUND: Complex regional pain syndrome type 1 (CRPS-1) is a rare, disabling and sometimes chronic disorder usually arising after a trauma. This exploratory study examined whether patients with chronic CRPS-1 have a different genetic profile compared with those who do not have the condition. METHODS: Exome sequencing was performed to seek altered non-synonymous SNP allele frequencies in a discovery cohort of well-characterised patients with chronic CRPS-1 (n=34) compared with population databases. Identified SNP alleles were confirmed by Sanger sequencing and sought in a replication cohort (n=50). Gene expression of peripheral blood macrophages was assessed. RESULTS: In the discovery cohort, the rare allele frequencies of four non-synonymous SNPs were statistically increased. The replication cohort confirmed this finding. In a chronic pain cohort, these alleles were not overexpressed. In total, 25 out of 84 (29.8%) patients with CRPS-1 expressed a rare allele. The SNPs were rs41289586 in ANO10, rs28360457 in P2RX7, rs1126930 in PRKAG1 and rs80308281 in SLC12A9. Males were more likely than females to have a rare SNP allele, 8 out of 14 (57.1%) vs 17 out of 70 (24.3%) (Fisher's p=0.023). ANO10, P2RX7, PRKAG1 and SLC12A9 were all expressed in macrophages from healthy human controls. CONCLUSION: A single SNP in each of the genes ANO10, P2RX7, PRKAG1 and SLC12A9 was associated with developing chronic CRPS-1, with more males than females expressing these rare alleles. Our work suggests the possibility that a permissive genetic background is an important factor in the development of CRPS-1.

Midfacial toddler excoriation syndrome (MiTES): case series, diagnostic criteria and evidence for a pathogenic mechanism.

BACKGROUND: PRDM12 polyalanine tract expansions cause two different disorders: midfacial toddler excoriation syndrome (MiTES; itch with normal pain sensation associated with 18 homozygous alanines (18A); and congenital insensitivity to pain (CIP) with normal itch associated with 19 homozygous alanines (19A). Knowledge of the phenotype, genotype and disease mechanism of MiTES is incomplete. Why 18A vs. 19A PRDM12 can cause almost opposite phenotypes is unknown; no other polyalanine or polyglutamine tract expansion disease causes two such disparate phenotypes. OBJECTIVES: To assess the genotype and phenotype of nine new, nine atypical and six previously reported patients diagnosed with MiTES. METHODS: Using cell lines with homozygous PR domain zinc finger protein 12 (PRDM12) containing 12 alanines (12A; normal), 18A (MiTES) and 19A (CIP), we examined PRDM12 aggregation and subcellular localization by image-separation confocal microscopy and subcellular fractionation Western blotting. RESULTS: MiTES presents in the first year of life; in all cases the condition regresses over the first decade, leaving scarring. The MiTES phenotype is highly distinctive. Features overlapping with PRDM12 CIP are rarely found. The genotype-phenotype study of the PRDM12 polyalanine tract shows that having 7-15 alanines is normal; 16-18 alanines is associated with MiTES; 19 alanines leads to CIP; and no clinically atypical cases of MiTES had a polyalanine tract expansion. PRDM12 aggregation and subcellular localization differed significantly between 18A and normal 12A cell lines and between 18A and 19A cell lines. MiTES is a new protein-aggregation disease. CONCLUSIONS: We provide diagnostic criteria for MiTES and improved longitudinal data. MiTES and CIP are distinct phenotypes, despite their genotypes varying by a single alanine in the PRDM12 polyalanine tract. We found clear distinctions between the cellular phenotypes of normal, MiTES and CIP cells. We hypothesize that the developmental environment of the trigeminal ganglion is unique and critically sensitive to pre- and postnatal levels of PRDM12.

Midfacial toddler excoriation syndrome (MiTES) causes facial itching and scratching in babies during their first year of life. MiTES tends to improve over the time period of approximately 10 years, but it can leave scars. Congenital insensitivity to pain (CIP) is a condition where a person cannot feel pain and is present from birth. This study looked at two conditions: MiTES and CIP. We specifically investigated changes in a gene called PRDM12, focusing on a part of the gene called the polyalanine tract ­ a sequence of many alanines (alanine is a type of amino acid). We discovered that the normal range for this sequence is between 7 and 15 alanines. If there are 16 to 18 alanines, it is associated with MiTES and causes the PRDM12 protein to clump together inside the cell. However, if there are 19 alanines, it leads to CIP, and the PRDM12 protein clumps together and moves to the cytoplasm, where it should not be. We found new evidence to suggest that MiTES is a disease where proteins clump together. Overall, our study findings show that despite there only being a small change in the same gene, MiTES and CIP are very different conditions.

Mutations in phospholipase C eta-1 (PLCH1) are associated with holoprosencephaly.

BACKGROUND: Holoprosencephaly is a spectrum of developmental disorder of the embryonic forebrain in which there is failed or incomplete separation of the prosencephalon into two cerebral hemispheres. To date, dominant mutations in sonic hedgehog (SHH) pathway genes are the predominant Mendelian causes, and have marked interfamilial and intrafamilial phenotypical variabilities. METHODS: We describe two families in which offspring had holoprosencephaly spectrum and homozygous predicted-deleterious variants in phospholipase C eta-1 (PLCH1). Immunocytochemistry was used to examine the expression pattern of PLCH1 in human embryos. We used SHH as a marker of developmental stage and of early embryonic anatomy. RESULTS: In the first family, two siblings had congenital hydrocephalus, significant developmental delay and a monoventricle or fused thalami with a homozygous PLCH1 c.2065C>T, p.(Arg689*) variant. In the second family, two siblings had alobar holoprosencephaly and cyclopia with a homozygous PLCH1 c.4235delA, p.(Cys1079ValfsTer16) variant. All parents were healthy carriers, with no holoprosencephaly spectrum features. We found that the subcellular localisation of PLCH1 is cytoplasmic, but the p.(Cys1079ValfsTer16) variant was predominantly nuclear. Human embryo immunohistochemistry showed PLCH1 to be expressed in the notorcord, developing spinal cord (in a ventral to dorsal gradient), dorsal root ganglia, cerebellum and dermatomyosome, all tissues producing or responding to SHH. Furthermore, the embryonic subcellular localisation of PLCH1 was exclusively cytoplasmic, supporting protein mislocalisation contributing to the pathogenicity of the p.(Cys1079ValfsTer16) variant. CONCLUSION: Our data support the contention that PLCH1 has a role in prenatal mammalian neurodevelopment, and deleterious variants cause a clinically variable holoprosencephaly spectrum phenotype.

Role of heat shock transcription factor 2 in the NMDA-dependent neuroplasticity induced by chronic ethanol intake in mouse hippocampus.

Ethanol consumption impairs learning and memory through disturbances of NMDA-type glutamate receptor-dependent synaptic plasticity (long-term depression [LTD] and long-term potentiation [LTP]) in the hippocampus. Recently, we demonstrated that two ethanol binge-like episodes in young adult rats selectively blocked NMDA-LTD in hippocampal slices, increased NMDA receptor sensitivity to a GluN2B subunit antagonist, and induced cognitive deficits. Here, using knockout adult mice, we show that a stress-responsive transcription factor of the heat shock factor family, HSF2, which is involved in the perturbation of brain development induced by ethanol, participates in these processes. In the absence of ethanol, hsf2-/- mice show a selective loss of LTD in the hippocampus, which is associated with an increased sensitivity of NMDA-field excitatory postsynaptic potentials (fEPSPs) to a GluN2B antagonist, compared with wild-type (WT) mice. These results suggest that HSF2 is required for proper glutamatergic synaptic transmission and LTD plasticity. After 1 month of chronic ethanol consumption in a two-bottle choice paradigm, WT mice showed an increase in hippocampal synaptic transmission, an enhanced sensitivity to GluN2B antagonist, and a blockade of LTD. In contrast, such modulation of synaptic transmission and plasticity were absent in hsf2-/- mice. We conclude that HSF2 is an important mediator of both glutamatergic neurotransmission and synaptic plasticity in basal conditions and also mediates ethanol-induced neuroadaptations of the hippocampus network after chronic ethanol intake.

Understanding the genetic basis of congenital insensitivity to pain.

INTRODUCTION OR BACKGROUND: Congenital insensitivity to pain (CIP) is caused by extremely rare Mendelian genetic disorders. CIP individuals demonstrate the unexpectedly severe consequences of painlessness. Although only a small number of causative conditions and genes are known, most have led to profound insights into human nociception. CIP gene discovery is catalyzing the manufacture of completely new classes of analgesics, and these are needed as alternatives to synthetic highly potent opioids. SOURCES OF DATA: Pubmed.gov peer-reviewed journal articles and reviews. AREAS OF AGREEMENT: The importance of nerve growth factor-tropomyosin receptor kinase A (NGF-TRKA) signalling for nociceptor genesis and subsequent pain sensing.New analgesics can be generated from knowledge of the NGF-TRKA nociceptor pathway.Increased susceptibility to Staphylococcus aureus infection is a consequence of deficient NGF-TRKA signalling.Mutations in the voltage-gated sodium channels SCN9A and SCN11A can cause congenital painlessness, and in contradistinction, other mutations can cause episodic neuropathic pain. SCN9A/Nav1.7 is an analgesic target. SCN11A/Nav1.9 is unlikely to be an analgesic target.There are further Mendelian causes of painlessness to be discovered. AREAS OF CONTROVERSY: Which NGF-TRKA intracellular signalling pathways operate in nociceptor development and which in post-natal pain sensing?Why have no clinically effective Nav1.7 antagonist been generated? SCN9A-CIP causes analgesia, at least in part, through endogenous opioids.Why do all CIP phenotypes involve a complete loss of all types of nociception? AREAS TIMELY FOR DEVELOPING RESEARCH: PRDM12 as an analgesic target.Discovery of the function and analgesic potential of new CIP genes.Can NGF-TRKA be used in the treatment of S. aureus?

Memory and plasticity impairment after binge drinking in adolescent rat hippocampus: GluN2A/GluN2B NMDA receptor subunits imbalance through HDAC2.

Ethanol (EtOH) induces cognitive impairment through modulation of synaptic plasticity notably in the hippocampus. The cellular mechanism(s) of these EtOH effects may range from synaptic signaling modulation to alterations of the epigenome. Previously, we reported that two binge-like exposures to EtOH (3 g/kg, ip, 9 h apart) in adolescent rats abolished long-term synaptic depression (LTD) in hippocampus slices, induced learning deficits, and increased N-methyl-d-aspartate (NMDA) receptor signaling through its GluN2B subunit after 48 hours. Here, we tested the hypothesis of EtOH-induced epigenetic alterations leading to modulation of GluN2B and GluN2A NMDA receptor subunits. Forty-two days old rats were treated with EtOH or the histone deacetylase inhibitor (HDACi) sodium butyrate (NaB, 600 mg/kg, ip) injected alone or 30 minutes before EtOH. After 48 hours, learning was tested with novel object recognition while synaptic plasticity and the role of GluN2A and GluN2B subunits in NMDA-fEPSP were measured in CA1 field of hippocampus slices. LTD and memory were impaired 48 hours after EtOH and NMDA-fEPSP analysis unraveled changes in the GluN2A/GluN2B balance. These results were associated with an increase in histone deacetylase (HDAC) activity and HDAC2 mRNA and protein while Ac-H4K12 labelling was decreased. EtOH increases expression of HDAC2 and mRNA level for GluN2B subunit (but not GluN2A), while HDAC2 modulates the promoter of the gene encoding GluN2B. Interestingly, NaB pretreatment prevented all the cellular and memory-impairing effects of EtOH. In conclusion, the memory-impairing effects of two binge-like EtOH exposure involve NMDA receptor-dependent LTD deficits due to a GluN2A/GluN2B imbalance resulting from changes in GluN2B expression induced by HDAC2.

Human Labor Pain Is Influenced by the Voltage-Gated Potassium Channel KV6.4 Subunit.

By studying healthy women who do not request analgesia during their first delivery, we investigate genetic effects on labor pain. Such women have normal sensory and psychometric test results, except for significantly higher cuff pressure pain. We find an excess of heterozygotes carrying the rare allele of SNP rs140124801 in KCNG4. The rare variant KV6.4-Met419 has a dominant-negative effect and cannot modulate the voltage dependence of KV2.1 inactivation because it fails to traffic to the plasma membrane. In vivo, Kcng4 (KV6.4) expression occurs in 40% of retrograde-labeled mouse uterine sensory neurons, all of which express KV2.1, and over 90% express the nociceptor genes Trpv1 and Scn10a. In neurons overexpressing KV6.4-Met419, the voltage dependence of inactivation for KV2.1 is more depolarized compared with neurons overexpressing KV6.4. Finally, KV6.4-Met419-overexpressing neurons have a higher action potential threshold. We conclude that KV6.4 can influence human labor pain by modulating the excitability of uterine nociceptors.