Biology subjects

Jain, R. P.

Publications and source records attributed to Jain, R. P..

4 recordsLinked to original sources

bioRxiv2025

From patterning to secretion: Kv2.1 subunits as regulators of zebrafish hatching gland morphogenesis and function

Zebrafish hatching, a critical developmental milestone, occurs around 48-72 hours post-fertilization (hpf). It is regulated by the specialized secretory organ called the hatching gland. Voltage-gated potassium channels (Kv) are known for their roles in maintaining plasma membrane potential and regulating intracellular protein traffic and secretion. Previous studies on zebrafish mutants of Kv2.1 channel subunits - the electrically active subunit Kcnb1 and the modulatory subunit Kcng4b - revealed antagonistic functions in the development of brain ventricles, ear, and Reissner fiber. In this study, we investigated their functional role in the hatching gland. The loss of either subunit resulted in a significant delay in normal hatching. Using in situ hybridization and immunohistochemistry, we show that both mutants exhibited severe defects in the hatching gland patterning, including a reduced number of hatching gland cells. The mutants displayed changes in the transcript levels of several hatching gland markers and reduced cell proliferation in this organ. These developmental defects were intensified by a late-stage functional failure characterized by decreased cathepsin synthesis, reduced proteolytic activity, and delay in the period of secretion in both mutants. Together, our findings establish that Kv2.1 subunits, Kcnb1, and Kcng4b are essential during the development of the zebrafish hatching gland and its secretion.

developmental biology↗

bioRxiv2025

Kv2.1-Kv6.4 subunits deficiency impairs inhibitory signaling and visual circuit dynamics in zebrafish

Voltage-gated potassium channels (Kv) play a crucial role in maintaining the cells resting potential. Mutations in the Kv2.1 voltage-gated potassium channel are associated with developmental epileptic encephalopathy. Previous analysis of the loss-of-function zebrafish mutants kcnb1sq301 and kcng4bwaw304, which affect genes that encode Kv2.1 subunits (the subunit Kcnb1 and the modulatory subunit Kcng4b), has shown that they play an antagonistic role in the development of hollow organs, such as the brain and ear. In this study, we investigated the behavioral effects of these mutations. Under normal light conditions, both mutants exhibited reduced activity at 5 days post-fertilization. However, exposure to a low concentration of 5 mM of the chemoconvulsant pentylenetetrazole increased their locomotor activity and induced seizures. Quantitative RT-PCR (qRT-PCR) analysis of the mutants revealed an increase in the transcript levels of c-fos and gad2, and a decrease in a transcript level of gabra1. This suggests that mutations cause a disruption to inhibitory neurotransmission. Local field potential recordings from the optic tectum of the mutants under baseline conditions showed an increase in spontaneous electrical activity. The kcnb1 mutant is photosensitive and experiences freezing episodes under high-intensity light. Together, these findings suggest that defects in Kv2.1 subunits impact both locomotor behavior and light-evoked responses.

developmental biology↗

bioRxiv2024

Kcnb1-Kcng4 axis regulates Scospondin secretion and Reissner fiber development

The voltage-gated potassium channel Kv2.1 plays a role in the development of the ventricular system and the subcommissural organ in zebrafish. Here, a role for Kv2.1 in the secretion of the major component of Reissners fiber, Scospondin, was demonstrated. The results showed that Kv2.1 acts as a negative regulator of Scospondin secretion and Reissner fiber assembly. Kv2.1 regulates formation of Scospondin microfilaments and their assembly in Reissner fiber. Cholesterol playing a key role in Scospondin secretion. After the Reissner fiber is formed, it is detached from the hindbrain floor plate, where Scospondin produced initially. The tension of the fiber depends on its attachment to the subcommissural and flexural organs. In turn fiber tension affects the morphogenesis of these organs. This process of Reissner fiber formation depends on the input provided by the Hedgehog and Wnt/{beta}-catenin signaling pathways on the anterior roof and floor plates.

developmental biology↗

bioRxiv2023

The Neuroprotective Effect of Short-chain Fatty Acids Against Hypoxia-reperfusion Injury

Gut microbe-derived short-chain fatty acids (SCFAs) are known to have a profound impact on various brain functions, including cognition, mood, and overall neurological health. However, their role, if any, in protecting against hypoxic injury and ischemic stroke has not been extensively studied. In this study, we investigated the effects of two major SCFAs abundant in the gut, propionate (P) and butyrate (B), on hypoxia-reperfusion injury using a neuronal cell line and a zebrafish model. Neuro 2a (N2a) cells treated with P and B exhibited reduced levels of mitochondrial and cytosolic reactive oxygen species (ROS), diminished loss of mitochondrial membrane potential, suppressed caspase activation, and lower rates of cell death when exposed to CoCl2-induced hypoxia, compared to the control group. Furthermore, adult zebrafish fed with SCFAs-supplemented feeds showed less susceptibility to hypoxic conditions compared to the control group, as indicated by multiple behavioral measures. Histological analysis of TTC-stained brain sections revealed lesser damage in the SCFAs-fed group. We also found that FABP7 (also known as BLBP), a neuroprotective fatty acid binding protein, was upregulated in the brains of the SCFAs-fed group. Additionally, when FABP7 was overexpressed in N2a cells, it protected the cells from hypoxia-reperfusion injury. Overall, our data clearly demonstrates a neuroprotective role of P and B against hypoxic brain injury and suggests the potential of dietary supplementation with SCFAs to mitigate stroke-induced brain damage. HighlightsO_LIShort-chain fatty acid (SCFA) Propionate (P) and Butyrate (B) protect N2a cells from hypoxia-reperfusion. C_LIO_LIZebrafish, when fed an SCFA-supplemented diet, are more resilient to hypoxia-reperfusion. C_LIO_LISCFAs in the diet boost brain expression of FABP7 (fatty acid binding protein). C_LIO_LIFABP7 overexpression in N2a cells provides protection against hypoxia-reperfusion. C_LIO_LISCFAs reduce reactive oxygen species (ROS) levels and increase FABP7, contributing to neuroprotection. C_LI

neuroscience↗