Biochemical and Biophysical Research Communications
Pannexin 1 deficiency can induce hearing loss
Introduction
As a gene family to encode gap junctional proteins in vertebrates, Pannexin (Panx1) was identified 10 years ago [1], [2]. So far, three pannexin isoforms (Panx1, 2, and 3) have been cloned from the human and mouse genomes [2]. Despite the lack of similar sequences with connexins, pannexin proteins share large similarities at the structural and functional levels [3]. They have been found to play important and critical roles in many physiological and pathological processes, such as ATP release [4], [5], Ca2+ homeostasis [6], [7], release of synaptic neurotransmitters [8], mediation of cell apoptosis [9], [10], and immunological response [11]. However, pannexin functions in vivo still remain largely undetermined.
It has been well-demonstrated that gap junctions play a critical role in hearing. Connexin (Cx) gene mutations can induce a high incidence of hearing loss [12], [13]. Cx26 and Cx30 have extensive expression in the cochlea [14], [15], [16]. Deletion of Cx26 in the cochlea can induce hearing loss [17], [18], [19], [20], [21], [22]. Like connexins, pannexins are also extensively expressed in the inner ear [23]. In particular, high expression of Panx1 was found in the cochlear spiral limbus (SLM), supporting cells in the organ of Corti (OC), and fibrocytes in the cochlear lateral wall [23]. In this study, we used Panx1 deficient mice to examine the function of Panx1 in the cochlea and hearing. We found that deletion of Panx1 in the cochlea can induce hearing loss. This study provides important information about the pannexin function in hearing.
Section snippets
Creation of Panx1 knockout mice
Panx1tm1a(KOMP)Wtsi knockout first mice were purchased from KOMP (Knock Out Mouse Project) and crossed with Pax2-Cre transgenic mouse line (the Mutation Mouse Regional Center, Chapel Hill, NC) to generate Panx1 conditional knockout (KO) in the cochlea. The mouse genotyping was identified by PCR amplification with the following primers: Panx1-Mut1a: 5′-CAC TGC ATT CTA GTT GTG GTT TGT CC-3′, Panx1-Mut2 (gene specific primer): 5′-CTG GCT CTC ATA ATT CTT GCC CTG-3′, Panx1-WF (wildtype-F): 5′-CTG
Deletion of Panx1 in the cochlea
As shown in our previous study [23], Panx1 had strong labeling in the organ of Corti (OC), the spiral limbus (SLM), and the cochlear lateral wall (Fig. 1A). In Panx1 KO mice, Panx1 expression in the SLM was completely deleted (Fig. 1B). Most of Panx1 expression in the cochlea and the cochlear lateral wall were also deleted. Only small, scattered Panx1 labeling was visible. The labeling was also light (Fig. 1B). In addition, the cochlea appeared normal development (Fig. 1B).
Hearing loss in Panx1 KO mice
Fig. 2 shows that
Conflict of interest
There is no conflict of interest.
Acknowledgments
We are grateful to Dr. Gerhard Dahl at Miami University for kindly providing anti-Panx1 antibody. This work was supported by a grant (R01) from the National Institute on Deafness and Other Communication Disorders, DC 05989.
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2022, ToxicologyCitation Excerpt :Several mechanisms underlie Panx1 channel opening, including increases in extracellular potassium and intracellular calcium concentration, phosphorylation and mechanical stimulation (Yang et al., 2022). Panx1 channels play essential roles in some physiological processes, such as in mucociliary clearance in the lungs (Ransford et al., 2009) and cochlear potassium recycling in the ears (Zhao et al., 2015). Whole-body Panx1 knock-out mice are viable with specific phenotypic changes, such as increased fibrosis and delayed wound healing (Penuela et al., 2014), increased number and size of spontaneous co-active cortical neuron network ensemble (Sanchez-Arias et al., 2019), altered susceptibility to atrial fibrillation (Petric et al., 2016) and liver injury (Willebrords et al., 2018).
Connexin hemichannels and cochlear function
2019, Neuroscience LettersCitation Excerpt :Thus, various conditions may activate Cx hemichannels, separate from reductions in extracellular Ca2+. A final point on pannexins in the cochlea, conditional deletion of Panx1 using mice from KOMP (UC Davis, CA) and foxg1-Cre or pax2-Cre mouse line to drive deletion was reported to cause moderate to severe hearing loss [40]. However, another study found no hearing deficits in Panx1 null mice, generated by Genentech (San Francisco, CA) and a ubiquitously active Cre deleter mouse to achieve widespread deletion of Panx1[41].
Pannexins in vision, hearing, olfaction and taste
2019, Neuroscience LettersCitation Excerpt :The conditions identified in the first clinical PANX1 patient are probably best reflected by the conditional mouse Panx1 KO model, providing insight into the consequences of loss of Panx1 along the entire auditory pathway during development and in adult animals [1]. In contrast, cell-specific ablation of Panx1 appears to be adding value in providing detailed insight into the consequences of a Panx1 loss in specific subsets of cells [101]. Together, the above-mentioned original reports have the ability to motivate ongoing research in the functions of pannexins in hearing.
Multiple and complex influences of connexins and pannexins on cell death
2018, Biochimica et Biophysica Acta - BiomembranesCitation Excerpt :However, other studies also suggest that, on the opposite, hemichannels may also play an important role in cell survival. First of all, in cochlea cells, Panx1 depletion activates caspase 3-dependant apoptosis [120]. Moreover, Cx43-based hemichannels were found involved in the anti-apoptotic effect of bisphosphonates in osteocyte and osteoblast.
Pannexin-2-deficiency sensitizes pancreatic β-cells to cytokine-induced apoptosis in vitro and impairs glucose tolerance in vivo
2017, Molecular and Cellular EndocrinologyPannexin1 as mediator of inflammation and cell death
2017, Biochimica et Biophysica Acta - Molecular Cell ResearchCitation Excerpt :In this respect, mice deficient in Panx1 display distinct behavioral changes, including enhanced anxiety, impaired object recognition and spatial learning [141]. Moreover, mice with conditional Panx1 knock-out in the cochlea show hearing loss [142]. This is reminiscent of a recent report describing sensorineural hearing loss, intellectual disability and skeletal defects, such as kyphoscoliosis and primary ovarian failure, in a 17-year-old female with a homozygous mutation in the Panx1 gene, whereby arginine at position 217 is replaced by histidine.