HTN1

The symbol HTN1 in the available corpus maps to multiple unrelated genes across organisms, and the discoveries fragment into at least three distinct proteins. The best-evidenced cluster describes the maize Htn1 locus, which encodes ZmWAK-RLK1, a plasma membrane-localized wall-associated receptor-like kinase with a non-RD kinase domain typical of plant innate immune receptors; loss-of-function TILLING mutants increase susceptibility to northern corn leaf blight, establishing it as the causal resistance gene (PMID:26124097). ZmWAK-RLK1 reduces pathogen penetration into host tissue and reprograms benzoxazinoid (BX) secondary metabolite biosynthesis, lowering BX content including DIM2BOA-Glc, with BX-biosynthesis mutants themselves showing increased resistance, linking Htn1-mediated defense to BX metabolite flux (PMID:30178602). Ht2 and Ht3 are allelic variants of this same gene that differ in their extracellular domains and thereby confer distinct race spectra (PMID:33533097). Separately, the human HTN1 entries describe histatin 1, a salivary antimicrobial peptide detectable in saliva by mass spectrometry (PMID:41223295) whose epithelial expression in allergic fungal rhinosinusitis is downregulated downstream of IL-6/STAT3-dependent TH17/TH22 signaling and is restored by exogenous IL-22/IL-17 stimulation (PMID:39032670). A yeast gene also named HTN1, identified only by sequence homology to mammalian RanBP1, and a huntingtin fragment study using the Htn label, are unrelated to these and to each other (PMID:7948031, PMID:19705452). Because these clusters describe fundamentally different proteins, no single unified mechanism can be synthesized; each is summarized within its own evidence cluster above.

1. 1994 Low

   An early entry under the HTN1 symbol described a yeast gene homologous to mammalian RanBP1, raising the possibility of a Ran-pathway signalling role.

   Evidence Gene cloning, sequencing, and sequence homology analysis in S. cerevisiae

   PMID:7948031

   Open questions at the time

   • No direct binding or functional experiment performed for the yeast protein
   • Interaction with GSP1/GSP2/PRP20 inferred from homology only
   • Unrelated to the maize and human HTN1 entries
2. 2010 Medium

   A study using the Htn1 label addressed whether a G-quartet oligonucleotide could bind and inhibit aggregation of an expanded-polyglutamine huntingtin fragment, with selectivity for the aggregation-prone form.

   Evidence Native gel, AGERA, pull-down, and atomic force microscopy on Htn1-171 Q58 versus Q23 fragments

   PMID:19705452

   Open questions at the time

   • Concerns a huntingtin polyQ fragment, not the salivary or maize HTN1 gene products
   • In vitro binding only; cellular relevance not established
3. 2015 High

   Map-based cloning resolved which gene underlies maize Htn1 northern corn leaf blight resistance, identifying ZmWAK-RLK1 and establishing it as a non-RD receptor-like kinase causal for the phenotype.

   Evidence Map-based cloning, TILLING loss-of-function mutants tested in greenhouse and field, splice-variant analysis

   PMID:26124097

   Open questions at the time

   • Ligand/elicitor recognized by the extracellular domain unknown
   • Kinase substrates and downstream signalling partners not identified
   • Mechanism of the truncated splice variant's effect unresolved
4. 2018 High

   Localization and near-isogenic-line transcriptomics defined how ZmWAK-RLK1 acts, placing it at the plasma membrane and linking resistance to reduced pathogen penetration and altered benzoxazinoid metabolite flux.

   Evidence Subcellular localization, transcriptome profiling of NILs, metabolite quantification, and BX-biosynthesis mutant epistasis

   PMID:30178602

   Open questions at the time

   • Direct biochemical link between kinase activity and BX gene regulation not established
   • Whether BX changes are cause or consequence of reduced penetration unresolved
5. 2021 High

   Allele analysis resolved whether Ht2 and Ht3 are independent resistance loci, showing they are variants of the same ZmWAK-RLK1 gene differing in the extracellular domain and accounting for distinct race specificities.

   Evidence Map-based cloning, TILLING mutants, and diversity/allele comparison

   PMID:33533097

   Open questions at the time

   • Structural basis of extracellular-domain race specificity not determined
   • No direct recognition assay for any race-specific elicitor
6. 2024 Medium

   Work on human histatin 1 positioned HTN1 within mucosal immunity, showing its epithelial expression is downregulated in allergic fungal rhinosinusitis downstream of defective IL-6/STAT3-driven TH17/TH22 signaling and restorable by IL-22/IL-17.

   Evidence RT-PCR, fungistasis assay, flow cytometry for TH17/TH22 and STAT signaling, in vitro IL-22/IL-17 epithelial stimulation in patient samples

   PMID:39032670

   Open questions at the time

   • Direct transcriptional regulators of HTN1 downstream of IL-22/IL-17 not mapped
   • Antimicrobial mechanism of the peptide itself not assayed here
   • Single-lab patient cohort
7. 2025 Low

   Targeted proteomics confirmed histatin 1 protein in saliva, validating its expression and enabling forensic body-fluid identification.

   Evidence Targeted DDA mass spectrometry with peptide standards and a 168-sample forensic validation set

   PMID:41223295

   Open questions at the time

   • Detection only; no functional mechanism tested
   • Does not address regulation or activity of the peptide

• The HTN1 symbol in this corpus conflates several biologically unrelated entities, and no cross-cutting mechanism unifies the maize receptor kinase, human salivary histatin, yeast RanBP1 homologue, and huntingtin-fragment entries.
• Reader must disambiguate which organism/gene each finding refers to
• No shared molecular pathway links the clusters