Prokineticin 2 regulates the electrical activity of rat suprachiasmatic nuclei neurons

Retina-attached slice recording reveals light-triggered tonic GABA signaling in suprachiasmatic nucleus

Light is a powerful external cue modulating the biological rhythm of internal clock neurons in the suprachiasmatic nucleus (SCN). GABA signaling in SCN is critically involved in this process. Both phasic and tonic modes of GABA signaling exist in SCN. Of the two modes, the tonic mode of GABA signaling has been implicated in light-mediated synchrony of SCN neurons. However, modulatory effects of external light on tonic GABA signalling are yet to be explored. Here, we systematically characterized electrophysiological properties of the clock neurons and determined the spatio-temporal profiles of tonic GABA current. Based on the whole-cell patch-clamp recordings from 76 SCN neurons, the cells with large tonic GABA current (>15 pA) were more frequently found in dorsal SCN. Moreover, tonic GABA current in SCN was highly correlated with the frequency of spontaneous inhibitory postsynaptic current (sIPSC), raising a possibility that tonic GABA current is due to spill-over from synaptic release. Interestingly, tonic GABA current was inversely correlated with slice-to-patch time interval, suggesting a critical role of retinal light exposure in intact brain for an induction of tonic GABA current in SCN. To test this possibility, we obtained meticulously prepared retina-attached SCN slices and successfully recorded tonic and phasic GABA signaling in SCN neurons. For the first time, we observed an early-onset, long-lasting tonic GABA current, followed by a slow-onset, short-lasting increase in the phasic GABA frequency, upon direct light-illumination of the attached retina. This result provides the first evidence that external light cue can directly trigger both tonic and phasic GABA signaling in SCN cell. In conclusion, we propose tonic GABA as the key mediator of external light in SCN.

Single-cell transcriptomics of suprachiasmatic nuclei reveal a Prokineticin-driven circadian network

Circadian rhythms in mammals are governed by the hypothalamic suprachiasmatic nucleus (SCN), in which 20,000 clock cells are connected together into a powerful time‐keeping network. In the absence of network‐level cellular interactions, the SCN fails as a clock. The topology and specific roles of its distinct cell populations (nodes) that direct network functions are, however, not understood. To characterise its component cells and network structure, we conducted single‐cell sequencing of SCN organotypic slices and identified eleven distinct neuronal sub‐populations across circadian day and night. We defined neuropeptidergic signalling axes between these nodes, and built neuropeptide‐specific network topologies. This revealed their temporal plasticity, being up‐regulated in circadian day. Through intersectional genetics and real‐time imaging, we interrogated the contribution of the Prok2‐ProkR2 neuropeptidergic axis to network‐wide time‐keeping. We showed that Prok2‐ProkR2 signalling acts as a key regulator of SCN period and rhythmicity and contributes to defining the network‐level properties that underpin robust circadian co‐ordination. These results highlight the diverse and distinct contributions of neuropeptide‐modulated communication of temporal information across the SCN.

Pleiotropic effects of prokineticin 2 in the control of energy metabolism

Prokineticins are family of small proteins involved in many important biological processes including food intake and control of energy balance. The prokineticin 2 (PROK2) is expressed in several peripheral tissues and areas in the central nervous system. PROK2 activates G protein-coupled receptors, namely, prokineticin receptor 1 (PROKR1) and prokineticin receptor 2 (PROKR2). Preclinical models exhibiting disturbances of the PROK2 pathway (at the level of PROK2 or its receptors) are characterized by changes in food intake, feeding behavior and insulin sensitivity related to a dysfunction of the energy balance control. In Humans, mutations of PROK2 and PROKR2 genes are associated to the Kallmann syndrome (KS) that affects both the hormonal reproductive axis and the sense of smell and may also lead to obesity. Moreover, plasma PROK2 concentration has been correlated with various cardiometabolic risk factors and type 2 diabetes (T2D). The present review summarizes knowledge on PROK2 structure, signaling and function focusing on its role in control of food intake and energy homeostasis.

Prokineticin signaling in heart-brain developmental axis: Therapeutic options for heart and brain injuries

Heart and brain development occur simultaneously during the embryogenesis, and both organ development and injuries are interconnected. Early neuronal and cardiac injuries share mutual cellular events, such as angiogenesis and plasticity that could either delay disease progression or, in the long run, result in detrimental health effects. For this reason, the common mechanisms provide a new and previously undervalued window of opportunity for intervention. Because angiogenesis, cardiogenesis and neurogenesis are essential for the development and regeneration of the heart and brain, we discuss therein the role of prokineticin as an angiogenic neuropeptide in heart-brain development and injuries. We focus on the role of prokineticin signaling and the effect of drugs targeting prokineticin receptors in neuroprotection and cardioprotection, with a special emphasis on heart failure, neurodegenerativParkinson's disease and ischemic heart and brain injuries. Indeed, prokineticin triggers common pro-survival signaling pathway in heart and brain. Our review aims at stimulating researchers and clinicians in neurocardiology to focus on the role of prokineticin signaling in the reciprocal interaction between heart and brain. We hope to facilitate the discovery of new treatment strategies, acting in both heart and brain degenerative diseases.

Ion Channels Controlling Circadian Rhythms in Suprachiasmatic Nucleus Excitability

Animals synchronize to the environmental day-night cycle by means of an internal circadian clock in the brain. In mammals, this timekeeping mechanism is housed in the suprachiasmatic nucleus (SCN) of the hypothalamus and is entrained by light input from the retina. One output of the SCN is a neural code for circadian time, which arises from the collective activity of neurons within the SCN circuit and comprises two fundamental components: 1) periodic alterations in the spontaneous excitability of individual neurons that result in higher firing rates during the day and lower firing rates at night, and 2) synchronization of these cellular oscillations throughout the SCN. In this review, we summarize current evidence for the identity of ion channels in SCN neurons and the mechanisms by which they set the rhythmic parameters of the time code. During the day, voltage-dependent and independent Na⁺ and Ca²⁺ currents, as well as several K⁺ currents, contribute to increased membrane excitability and therefore higher firing frequency. At night, an increase in different K⁺ currents, including Ca²⁺-activated BK currents, contribute to membrane hyperpolarization and decreased firing. Layered on top of these intrinsically regulated changes in membrane excitability, more than a dozen neuromodulators influence action potential activity and rhythmicity in SCN neurons, facilitating both synchronization and plasticity of the neural code.

Overexpression of Prokineticin 2 in Transgenic Mice Leads to Reduced Circadian Behavioral Rhythmicity and Altered Molecular Rhythms in the Suprachiasmatic Clock

In mammals, the master pacemaker driving circadian rhythms is thought to reside in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. A clear view of molecular clock mechanisms within the SCN neurons has been elucidated. In contrast, much less is known about the output mechanism by which the SCN circadian pacemaker sends timing information for eventual control of physiological and behavioral rhythms. Two secreted molecules, prokineticin 2 (PK2) and vasopressin, that are encoded by respective clock-controlled genes, have been indicated as candidate SCN output molecules. Several lines of evidence have emerged that support the role of PK2 as an output signal for the SCN circadian clock, including the reduced circadian rhythms in mice that are deficient in PK2 or its receptor, PKR2. In the current study, transgenic mice with the overexpression of PK2 have been generated. These transgenic mice displayed reduced oscillation of the PK2 expression in the SCN and decreased amplitude of circadian locomotor rhythm, supporting the important signaling role of PK2 in the regulation of circadian rhythms. Altered molecular rhythms were also observed in the SCN in the transgenic mice, indicating that PK2 signaling also regulates the operation of core clockwork. This conclusion is consistent with recent reports showing the likely signaling role of PK2 from the intrinsically photosensitive retinal ganglion cells to SCN neurons. Thus, PK2 signaling plays roles in both the input and the output pathways of the SCN circadian clock.

The Prokineticins: Neuromodulators and Mediators of Inflammation and Myeloid Cell-Dependent Angiogenesis

The mammalian prokineticins family comprises two conserved proteins, EG-VEGF/PROK1 and Bv8/PROK2, and their two highly related G protein-coupled receptors, PKR1 and PKR2. This signaling system has been linked to several important biological functions, including gastrointestinal tract motility, regulation of circadian rhythms, neurogenesis, angiogenesis and cancer progression, hematopoiesis, and nociception. Mutations in PKR2 or Bv8/PROK2 have been associated with Kallmann syndrome, a developmental disorder characterized by defective olfactory bulb neurogenesis, impaired development of gonadotropin-releasing hormone neurons, and infertility. Also, Bv8/PROK2 is strongly upregulated in neutrophils and other inflammatory cells in response to granulocyte-colony stimulating factor or other myeloid growth factors and functions as a pronociceptive mediator in inflamed tissues as well as a regulator of myeloid cell-dependent tumor angiogenesis. Bv8/PROK2 has been also implicated in neuropathic pain. Anti-Bv8/PROK2 antibodies or small molecule PKR inhibitors ameliorate pain arising from tissue injury and inhibit angiogenesis and inflammation associated with tumors or some autoimmune disorders.

Temporal variations in presynaptic release probability in the lateral habenula

Rhythmicity plays an important role in a number of biological systems. The habenular complex is reported to contain an intrinsic molecular clock and to show rhythmic expression of circadian clock genes and proteins including per2/PER2. In this study, we observed that there is a temporal rhythmicity in the presynaptic efficacy of the lateral habenula (LHb) neurons. We collected a substantial number of recordings at different time points of the day during the light phase. The frequency and amplitude of spontaneous excitatory transmission were increased in the afternoon compared to recordings performed in the morning. In addition, the paired-pulse ratio and the success rate of minimal stimulation were also significantly different depending on the time of the recording. We did not see any significant differences in recordings obtained from pyramidal neurons of the hippocampus in the same brain slices. Taken together, our data indicates that the LHb exhibits intrinsic temporal oscillation in basal neurotransmission and in presynaptic release probability. Given the rapidly growing interest on the function of the LHb, more careful examination of synaptic transmission in the LHb is thus required.

Differential arousal regulation by prokineticin 2 signaling in the nocturnal mouse and the diurnal monkey

The temporal organization of activity/rest or sleep/wake rhythms for mammals is regulated by the interaction of light/dark cycle and circadian clocks. The neural and molecular mechanisms that confine the active phase to either day or night period for the diurnal and the nocturnal mammals are unclear. Here we report that prokineticin 2, previously shown as a circadian clock output molecule, is expressed in the intrinsically photosensitive retinal ganglion cells, and the expression of prokineticin 2 in the intrinsically photosensitive retinal ganglion cells is oscillatory in a clock-dependent manner. We further show that the prokineticin 2 signaling is required for the activity and arousal suppression by light in the mouse. Between the nocturnal mouse and the diurnal monkey, a signaling receptor for prokineticin 2 is differentially expressed in the retinorecipient suprachiasmatic nucleus and the superior colliculus, brain projection targets of the intrinsically photosensitive retinal ganglion cells. Blockade with a selective antagonist reveals the respectively inhibitory and stimulatory effect of prokineticin 2 signaling on the arousal levels for the nocturnal mouse and the diurnal monkey. Thus, the mammalian diurnality or nocturnality is likely determined by the differential signaling of prokineticin 2 from the intrinsically photosensitive retinal ganglion cells onto their retinorecipient brain targets.

Sustained Endocrine Gland-Derived Vascular Endothelial Growth Factor Levels Beyond the First Trimester of Pregnancy Display Phenotypic and Functional Changes Associated With the Pathogenesis of Pregnancy-Induced Hypertension

Pregnancy-induced hypertension diseases are classified as gestational hypertension, preeclampsia, or eclampsia. The mechanisms of their development and prediction are still to be discovered. Endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is an angiogenic factor secreted by the placenta during the first trimester of human pregnancy that was shown to control trophoblast invasion, to be upregulated by hypoxia, and to be abnormally elevated in pathological pregnancies complicated with preeclampsia and intrauterine growth restriction. These findings suggested that sustaining EG-VEGF levels beyond the first trimester of pregnancy may contribute to pregnancy-induced hypertension. To test this hypothesis, osmotic minipumps delivering EG-VEGF were implanted subcutaneously into gravid OF1 (Oncins France 1) mice on day 11.5 post coitus, which is equivalent to the end of the first trimester of human pregnancy. Mice were euthanized at 15.5 and 18.5 days post coitus to assess (1) litter size, placental, and fetal weights; (2) placental histology and function; (3) maternal blood pressure; (4) renal histology and function; and (5) circulating soluble fms-like tyrosine kinase 1 and soluble endoglin. Increased EG-VEGF levels caused significant defects in placental organization and function. Both increased hypoxia and decreased trophoblast invasion were observed. Treated mice had elevated circulating soluble fms-like tyrosine kinase 1 and soluble endoglin and developed gestational hypertension with dysregulated maternal kidney function. EG-VEGF effect on the kidney function was secondary to its effects on the placenta as similarly treated male mice had normal kidney functions. Altogether, these data provide a strong evidence to confirm that sustained EG-VEGF beyond the first trimester of pregnancy contributes to the development of pregnancy-induced hypertension.

Expression of prokineticin 2 and its receptor in the macaque monkey brain

Prokineticin 2 (PK2) has been indicated as an output signaling molecule for the suprachiasmatic nucleus (SCN) circadian clock. Most of these studies were performed with nocturnal animals, particularly mice and rats. In the current study, the PK2 and its receptor, PKR2, was cloned from a species of diurnal macaque monkey. The macaque monkey PK2 and PKR2 were found to be highly homologous to that of other mammalian species. The mRNA expression of PK2 and PKR2 in the macaque brain was examined by in situ hybridization. The expression patterns of PK2 and PKR2 in the macaque brain were found to be quite similar to that of the mouse brain. Particularly, PK2 mRNA was shown to oscillate in the SCN of the macaque brain in the same phase and with similar amplitude with that of nocturnal mouse brain. PKR2 expression was also detected in known primary SCN targets, including the midline thalamic and hypothalamic nuclei. In addition, we detected the expression of PKR2 mRNA in the dorsal raphe nucleus (DR) of both macaque and mouse brains. As a likely SCN to dorsal raphe projection has previously been indicated, the expression of PKR2 in the raphe nuclei of both macaque and mouse brain signifies a possible role of DR as a previously unrecognized primary SCN projection target.

Bv8/prokineticin 2 is involved in Aβ-induced neurotoxicity

Bv8/Prokineticin 2 (PROK2) is a bioactive peptide initially discovered as a regulator of gastrointestinal motility. Among multiple biological roles demonstrated for PROK2, it was recently established that PROK2 is an insult-inducible endangering mediator for cerebral damage. Aim of the present study was to evaluate the PROK2 and its receptors' potential involvement in amyloid beta (Aβ) neurotoxicity, a hallmark of Alzheimer's disease (AD) and various forms of traumatic brain injury (TBI). Analyzing primary cortical cultures (CNs) and cortex and hippocampus from Aβ treated rats, we found that PROK2 and its receptors PKR1 and PKR2 mRNA are up-regulated by Aβ, suggesting their potential involvement in AD. Hence we evaluated if impairing the prokineticin system activation might have protective effect against neuronal death induced by Aβ. We found that a PKR antagonist concentration-dependently protects CNs against Aβ(1-42)-induced neurotoxicity, by reducing the Aβ-induced PROK2 neuronal up-regulation. Moreover, the antagonist completely rescued LTP impairment in hippocampal slices from 6 month-old Tg2576 AD mice without affecting basal synaptic transmission and paired pulse-facilitation paradigms. These results indicate that PROK2 plays a role in cerebral amyloidosis and that PROK2 antagonists may represent a new approach for ameliorating the defining pathology of AD.

Rhythmic Trafficking of TRPV2 in the Suprachiasmatic Nucleus is Regulated by Prokineticin 2 Signaling

The mammalian circadian clock is composed of single-cell oscillators. Neurochemical and electrical signaling among these oscillators is important for the normal expression of circadian rhythms. Prokineticin 2 (PK2), encoding a cysteine-rich secreted protein, has been shown to be a critical signaling molecule for the regulation of circadian rhythms. PK2 expression in the suprachiasmatic nucleus (SCN) is highly rhythmic, peaking during the day and being essentially absent during the night. Mice with disrupted PK2 gene or its receptor PKR2 display greatly reduced rhythmicity of broad circadian parameters such as locomotor activity, body temperature and sleep/wake patterns. PK2 has been shown to increase the firing rate of SCN neurons, with unknown molecular mechanisms. Here we report that TRPV2, an ion channel belonging to the family of TRP, is co-expressed with PKR2 in the SCN neurons. Further, TRPV2 protein, but not TRPV2 mRNA, was shown to oscillate in the SCN in a PK2-dependent manner. Functional studies revealed that TRPV2 enhanced signaling of PKR2 in calcium mobilization or ion current conductance, likely via the increased trafficking of TRPV2 to the cell surface. Taken together, these results indicate that TRPV2 is likely part of the downstream signaling of PK2 in the regulation of the circadian rhythms.

Intrinsic and extrinsic cues regulate the daily profile of mouse lateral habenula neuronal activity

The epithalamic lateral habenula (LHb) is implicated as part of the mammalian brain's circadian system. Anatomical evidence suggests that the LHb receives extrinsic circadian timing cues from retinal ganglion cells and the master clock in the suprachiasmatic nuclei (SCN). Intriguingly, some LHb neurones contain the molecular circadian clock, but it is unclear if and how intrinsic and extrinsic circadian processes influence neuronal activity in the mouse LHb. Here, using an in vitro brain slice preparation isolating the LHb from the SCN, we show through whole-cell patch-clamp recordings that LHb neurones exhibit heterogeneity in their resting state, but the majority spontaneously fire action potentials (APs). Discharge rate of APs varied from low firing in the early day to higher firing later in the day and was absent in LHb brain slices prepared from Cry1(-/-)Cry2(-/-) mice that lack a functional molecular clock. Low amplitude circadian oscillations in the molecular circadian clock were also monitored in LHb brain slices, but were absent in Cry1(-/-)Cry2(-/-) LHb brain tissue. A putative neurochemical output signal of the SCN, prokineticin 2 (PK2), inhibited some LHb neurones by elevating the frequency of GABA release in the LHb. Using multi-electrode recordings in vivo, we found that LHb neurones sluggishly respond to retinal illumination, suggesting that they receive such information through polysynaptic processes. In summary, our results show for the first time that intrinsic circadian signals are important for regulating LHb neuronal state, while the SCN-derived signal PK2 is less influential. Moreover, we demonstrate that mouse LHb neurones have access to and can respond to visual input, but such signals are unlikely to be directly communicated to the LHb. Broadly, these findings raise the possibility that intrinsic circadian signals are likely to be influential in shaping LHb contributions to cognition and emotionality.

Controlling the activation of the Bv8/prokineticin system reduces neuroinflammation and abolishes thermal and tactile hyperalgesia in neuropathic animals

BACKGROUND AND PURPOSE

Chemokines are involved in neuroinflammation and contribute to chronic pain processing. The new chemokine prokineticin 2 (PROK2) and its receptors (PKR1 and PKR2 ) have a role in inflammatory pain and immunomodulation. In the present study, we investigated the involvement of PROK2 and its receptors in neuropathic pain.

EXPERIMENTAL APPROACH

Effects of single, intrathecal, perineural and s.c. injections of the PKR antagonist PC1, or of 1 week s.c. treatment, on thermal hyperalgesia and tactile allodynia was evaluated in mice with chronic constriction of the sciatic nerve (CCI). Expression and localization of PROK2 and of its receptors at peripheral and central level was evaluated 10 days after CCI, following treatment for 1 week with saline or PC1. IL-1β and IL-10 levels, along with glia activation, were evaluated.

KEY RESULTS

Subcutaneous, intrathecal and perineural PC1 acutely abolished the CCI-induced hyperalgesia and allodynia. At 10 days after CCI, PROK2 and its receptor PKR2 were up-regulated in nociceptors, in Schwann cells and in activated astrocytes of the spinal cord. Therapeutic treatment with PC1 (s.c., 1 week) alleviated established thermal hyperalgesia and allodynia, reduced the injury-induced overexpression of PROK2, significantly blunted nerve injury-induced microgliosis and astrocyte activation in the spinal cord and restored the physiological levels of proinflammatory and anti-inflammatory cytokines in periphery and in spinal cord.

CONCLUSION AND IMPLICATIONS

The prokineticin system contributes to pain modulation via neuron-glia interaction. Sustained inhibition of the prokineticin system, at peripheral or central levels, blocked both pain symptoms and some events underlying disease progression.

Effects of Gelsemium sempervirens L. on pathway-focused gene expression profiling in neuronal cells

ETHNOPHARMACOLOGICAL RELEVANCE

Gelsemium sempervirens L. is a traditional medicinal plant mainly distributed in the southeastern of the United States, employed in phytotheraphy and homeopathy as nervous system relaxant to treat various types of anxiety, pain, headache and other ailments. Although animal models showed its effectiveness, the mechanisms by which it might operate on the nervous system are largely unknown. This study investigated for the first time by a real-time PCR technique (RT-PCR Array) the gene expression of a panel of human neurotransmitter receptors and regulators, involved in neuronal excitatory signaling, on a neurocyte cell line.

MATERIALS AND METHODS

Human SH-SY5Y neuroblastoma cells were exposed for 24h to Gelsemium sempervirens at 2c and 9c dilutions (i.e. 2 and 9-fold centesimal dilutions from mother tincture) and the gene expression profile compared to that of cells treated with control vehicle solutions.

RESULTS

Exposure to the Gelsemium sempervirens 2c dilution, containing a nanomolar concentration of active principle gelsemine, induced a down-regulation of most genes of this array. In particular, the treated cells showed a statistically significant decrease of the prokineticin receptor 2, whose ligand is a neuropeptide involved in nociception, anxiety and depression-like behavior.

CONCLUSIONS

Overall, the results indicate a negative modulation trend in neuronal excitatory signaling, which can suggest new working hypotheses on the anxiolytic and analgesic action of this plant.

Functional rescue of Kallmann syndrome-associated prokineticin receptor 2 (PKR2) mutants deficient in trafficking

Mutations in the G protein-coupled prokineticin receptor 2 (PKR2) are known to cause Kallmann syndrome and idiopathic hypogonadotropic hypogonadism manifesting with delayed puberty and infertility. Some of the mutant receptors are not routed to the cell surface; instead, they are trapped in the cellular secretory pathway. The cell-permeant agonists/antagonists have been used to rescue some membrane receptors that are not targeted onto the cell membrane. Here, we chose three disease-associated mutations (W178S, G234D, and P290S), which all resulted in retention of PKR2 intracellularly. We show that a small molecule PKR2 antagonist (A457) dramatically increased cell surface expression and rescued the function of P290S PKR2, but had no effect on W178S and G234D PKR2. Furthermore, we also tested chemical chaperone glycerol on the cell surface expression and function of PKR2 mutants. Treatment with 10% glycerol significantly increased the cell surface expression and signaling of P290S and W178S PKR2. These data demonstrate that some Kallmann syndrome-associated, intracellularly retained mutant PKR2 receptors can be functionally rescued, suggesting a potential treatment strategy for patients bearing such mutations.

Jr. WF, Hastings MH, Zhou QY. Signaling role of prokineticin 2 on the estrous cycle of female mice

The possible signaling role of prokineticin 2 (PK2) and its receptor, prokineticin receptor 2 (PKR2), on female reproduction was investigated. First, the expression of PKR2 and its co-localization with estrogen receptor (ERα) in the hypothalamus was examined. Sexually dimorphic expression of PKR2 in the preoptic area of the hypothalamus was observed. Compared to the male mice, there was more widespread PKR2 expression in the preoptic area of the hypothalamus in the female mice. The likely co-expression of PKR2 and ERα in the preoptic area of the hypothalamus was observed. The estrous cycles in female PK2-null, and PKR2-null heterozygous mice, as well as in PK2-null and PKR2-null compound heterozygous mice were examined. Loss of one copy of PK2 or PKR2 gene caused elongated and irregular estrous cycle in the female mice. The alterations in the estrous cycle were more pronounced in PK2-null and PKR2-null compound heterozygous mice. Consistent with these observations, administration of a small molecule PK2 receptor antagonist led to temporary blocking of estrous cycle at the proestrous phase in female mice. The administration of PKR2 antagonist was found to blunt the circulating LH levels. Taken together, these studies indicate PK2 signaling is required for the maintenance of normal female estrous cycles.

Absence of central circadian pacemaker abnormalities in humans with loss of function mutation in prokineticin 2

CONTEXT

Loss of prokineticin 2 (PROK2) signaling in mice disrupts circadian rhythms, but the role of PROK2 signaling in the regulation of circadian rhythms in humans is undetermined.

OBJECTIVE

The aim of the study was to examine the circadian rhythms of humans with a complete loss-of-function PROK2 mutation using an inpatient constant routine (CR) protocol.

DESIGN AND SETTING

We conducted a case study in an academic medical center.

SUBJECTS AND METHODS

Two siblings (one male and one female, ages 67 and 62 y, respectively) with isolated GnRH deficiency (IGD) due to a biallelic loss-of-function PROK2 mutation were studied using an inpatient CR protocol. Historical data from inpatient CR protocols conducted in healthy controls (ages 65-81 y) were used for comparison.

MAIN OUTCOME MEASURES

We measured circadian phase markers (melatonin, cortisol, and core body temperature) and neurobehavioral performance (psychomotor vigilance task [PVT] and subjective alertness scale).

RESULTS

Circadian waveforms of melatonin and cortisol did not differ between the IGD participants with PROK2 mutation and controls. In both IGD participants, neurobehavioral testing with PVT showed disproportionate worsening of PVT lapses and median reaction time in the second half of the CR.

CONCLUSIONS

Humans with loss of PROK2 signaling lack abnormalities in circadian phase markers, indicating intact central circadian pacemaker activity in these patients. These results suggest that PROK2 signaling in humans is not required for central circadian pacemaker function. However, impaired PVT in the PROK2-null participants despite preserved endocrine rhythms suggests that PROK2 may transmit circadian timing information to some neurobehavioral neural networks.

A transcriptome-wide screen for mRNAs enriched in fetal Leydig cells: CRHR1 agonism stimulates rat and mouse fetal testis steroidogenesis

Fetal testis steroidogenesis plays an important role in the reproductive development of the male fetus. While regulators of certain aspects of steroidogenesis are known, the initial driver of steroidogenesis in the human and rodent fetal testis is unclear. Through comparative analysis of rodent fetal testis microarray datasets, 54 candidate fetal Leydig cell-specific genes were identified. Fetal mouse testis interstitial expression of a subset of these genes with unknown expression (Crhr1, Gramd1b, Itih5, Vgll3, and Vsnl1) was verified by whole-mount in situ hybridization. Among the candidate fetal Leydig cell-specific factors, three receptors (CRHR1, PRLR, and PROKR2) were tested for a steroidogenic function using ex vivo fetal testes treated with receptor agonists (CRH, PRL, and PROK2). While PRL and PROK2 had no effect, CRH, at low (approximately 1 to 10) nM concentration, increased expression of the steroidogenic genes Cyp11a1, Cyp17a1, Scarb1, and Star in GD15 mouse and GD17 rat testes, and in conjunction, testosterone production was increased. Exposure of GD15 fetal mouse testis to a specific CRHR1 antagonist blunted the CRH-induced steroidogenic gene expression and testosterone responses. Similar to ex vivo rodent fetal testes, ≥10 nM CRH exposure of MA-10 Leydig cells increased steroidogenic pathway mRNA and progesterone levels, showing CRH can enhance steroidogenesis by directly targeting Leydig cells. Crh mRNA expression was observed in rodent fetal hypothalamus, and CRH peptide was detected in rodent amniotic fluid. Together, these data provide a resource for discovering factors controlling fetal Leydig cell biology and suggest that CRHR1 activation by CRH stimulates rat and mouse fetal Leydig cell steroidogenesis in vivo.