Loss of Neuron Navigator 2 Impairs Brain and Cerebellar Development.

Cerebellar hypoplasia and dysplasia encompass a group of clinically and genetically heterogeneous disorders frequently associated with neurodevelopmental impairment. The Neuron Navigator 2 (NAV2) gene (MIM: 607,026) encodes a member of the Neuron Navigator protein family, widely expressed within the central nervous system (CNS), and particularly abundant in the developing cerebellum. Evidence across different species supports a pivotal function of NAV2 in cytoskeletal dynamics and neurite outgrowth.

Expression pattern of Nav2 in the murine CNS with development.

Neuron navigator 2 (NAV2, RAINB1, POMFIL2, HELAD1, unc53H2) is essential for nervous system development. In the present study the spatial distribution of Nav2 transcript in mouse CNS during embryonic, postnatal and adult life is examined. Because multiple NAV2 proteins are predicted based on alternate promoter usage and RNA splicing, in situ hybridization was performed using probes designed to the 5' and 3' ends of the Nav2 transcript, and PCR products using primer sets spanning the length of the mRNA were also examined by real time PCR (qPCR).

A New 1,25 Dihydroxy Vitamin D Analog with Strong Bone Anabolic Activity in OVX Rats with Little or no Bone Resorptive Activity.

A new 1α,25-dihydroxy vitamin D analog (2-methylene-22(E)-(24R)-22-dehydro-1α,24,25-trihydroxy-19-norvitamin D or WT-51) has been tested as a possible therapeutic for osteoporosis. It is 1/10th as active as 1,25(OH) D in binding affinity for the vitamin D receptor but is at least 200 times more active than 1,25(OH) D and equal to that of 2MD (2-methylene-19-nor-(20S)-1α,25(OH) D , an analog previously tested in postmenopausal women), in supporting bone formation by isolated osteoblasts in culture. However, in contrast to 2MD, it is virtually inactive on bone resorption in vivo.

4-HPR Is an Endoplasmic Reticulum Stress Aggravator and Sensitizes Breast Cancer Cells Resistant to TRAIL/Apo2L.

Background/aim: N-(4-hydroxyphenyl)retinamide (4-HPR) is a synthetic retinoid, less toxic than the parent all-trans retinoic acid (RA). Unlike RA, 4-HPR induces apoptosis in tumor cells. Because 4-HPR can hydrolyze to liberate RA, a potent human teratogen, the unhydrolyzable ketone analog of 4-HPR, 4-hydroxybenzylretinone (4-HBR) has been prepared and has been found to cause apoptosis in tumor cells and shrink carcinogen-induced rat mammary tumors as 4-HPR does.

Differential activity of 2-methylene-19-nor vitamin D analogs on growth factor gene expression in rhino mouse skin and comparison to all-trans retinoic acid.

While all 2-methylene-19-nor analogs of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) tested produce an increase in epidermal thickness in the rhino mouse, only a subset reduce utricle size (comedolysis). All-trans retinoic acid (atRA) also causes epidermal thickening and a reduction in utricle size in the rhino mouse. We now report that 2-methylene-19-nor-(20S)-1α-hydroxybishomopregnacalciferol (2MbisP), a comedolytic analog, increases epidermal thickening more rapidly than does atRA, while both reduce utricle area at an equal rate.

Pharmacokinetics of a New Oral Vitamin D Receptor Activator (2-Methylene-19-Nor-(20S)-1α,25-Dihydroxyvitamin D) in Patients with Chronic Kidney Disease and Secondary Hyperparathyroidism on Hemodialysis.

Background: 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D (DP001 or 2MD) is a novel, potent 1α-hydroxylated vitamin D analog that binds to the vitamin D receptor and suppresses parathyroid hormone synthesis and secretion with potential for an improved safety profile compared to existing active vitamin D analogs. The purpose of this study was to evaluate the pharmacokinetics of DP001 given orally after hemodialysis.

Methods: DP001 (550 ng) was given orally to 11 hemodialysis patients with secondary hyperparathyroidism after each dialysis session (3 times/week) for 4 weeks.

2MD (DP001), a Single Agent in the Management of Hemodialysis Patients: A Randomized Trial.

Background: Vitamin D analogs and calcimimetics are used to manage secondary hyperparathyroidism (SHPT) in dialysis patients. DP001 is an oral vitamin D analog that suppresses parathyroid hormone (PTH) in uremic rats, osteopenic women, and hemodialysis patients. The safety and effectiveness of DP001 suppressing PTH in dialysis patients previously managed with active vitamin D with or without a calcimimetic are presented.

Use of 2MD, a Novel Oral Calcitriol Analog, in Hemodialysis Patients with Secondary Hyperparathyroidism.

Background: Use of existing therapies for secondary hyperparathyroidism (SHPT), such as calcitriol or paricalcitol, is frequently limited by the development of hypercalcemia. 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D3 (2MD; DP001) is a novel and a more potent vitamin D receptor activator (VDRA) that more selectively localizes in the parathyroid gland, and has a wider therapeutic margin in the uremic rat model than calcitriol and paricalcitol.

Design, Setting, Participants, And Measurements: Hemodialysis patients were enrolled and dosed with 110, 220, 330, 440, or 550 ng of 2MD orally thrice weekly for 4 weeks.

Improved Synthesis of the -Glucuronide/Glycoside of 4-Hydroxybenzylretinone (4-HBR).

Improvements in the synthesis of carbon-linked glucuronide/glucoside conjugates of cancer chemopreventive retinoids have been achieved starting with 2,3,4,6-tetra--benzyl-D-glucopyranose. The revised approach demonstrates better yields, eliminates the use of an expensive, carcinogenic protecting group reagent, and avoids much painstaking chromatography. The new approach should allow synthesis of larger quantities of the agents for detailed animal and mechanistic studies.

A complex RARE is required for the majority of Nedd9 embryonic expression.

Neural precursor cell expressed, developmentally down-regulated 9 (Nedd9, Casl, Hef1, p105cas, Ef1) is a scaffolding protein that assembles complexes involved in regulating cell adhesion, migration, division, and survival. Nedd9 is found very early in the developing embryonic nervous system. A highly conserved complex retinoic acid response element (RARE) is located 485 base pairs (bp) upstream of exon 2B in the promoter of the Nedd9 gene.

Novel, selective vitamin D analog suppresses parathyroid hormone in uremic animals and postmenopausal women.

Background: The use of 1α-hydroxylated vitamin D therapy to control secondary hyperparathyroidism in renal failure patients has been a success story, culminating with the demonstration of increased life expectancy in patients treated with these compounds. However, hypercalcemic episodes have been a recurrent problem with these therapies and have resulted in the added use of calcium mimetics. Clearly there is good reason to search for improved vitamin D therapy.

26-Desmethyl-2-methylene-22-ene-19-nor-1α,25-dihydroxyvitamin D3 compounds selectively active on intestine.

Six new analogs of 2-methylene-19-nor-1α,25-dihydroxyvitamin D3, 6-7 and 8a,b-9a,b, have been synthesized. All compounds are characterized by a trans double bond located in the side chain between C-22 and C-23. While compounds 6 and 7 possess C-26 and C-27 methyls, compounds 8a,b and 9a,b lack one of these groups.

14-3-3ε and NAV2 interact to regulate neurite outgrowth and axon elongation.

Neuron navigator 2 (NAV2) is required for all-trans retinoic acid (atRA) to induce neurite outgrowth in human neuroblastoma cells. Further, ectopic overexpression of full-length human NAV2 rescues an axonal elongation defect in the Caenorhabditis elegans unc-53 (NAV2 ortholog) mutant. Using a region of NAV2 that independently associates with the cytoskeleton as bait in a yeast-two-hybrid screen, 14-3-3ε was identified as a novel NAV2 interacting partner.

26- and 27-Methyl groups of 2-substituted, 19-nor-1α,25-dihydroxylated vitamin D compounds are essential for calcium mobilization in vivo.

Twelve new analogs of 19-nor-1α,25-dihydroxyvitamin D36-17, were prepared by a multi-step procedure from known alcohols 18 and 19. We have examined the influence of removing two methyl groups located at C-25, as well as the 25-hydroxy group, on the biological in vitro and in vivo biological activity. Surprisingly, removal of the 26- and 27-methyl groups from either the 2α-methyl or 2-methylene-19-nor-1α,25-dihydroxyvitamin D3 reduced vitamin D receptor binding, HL-60 differentiation, and 25-hydroxylase transcription in vitro only slightly to moderately (compounds 6-13).

Astrocytes as a regulated source of retinoic acid for the brain.

Retinaldehyde dehydrogenases (RALDH) catalyze the synthesis of the regulatory factor retinoic acid (RA). Cultured astrocytes express several of the RALDH enzyme family, and it has been assumed that this can be extrapolated to astrocytes in vivo. However, this study finds that few astrocytes in the rodent brain express detectable RALDH enzymes, and only when these cells are grown in culture are these enzymes upregulated.

A 20S combined with a 22R configuration markedly increases both in vivo and in vitro biological activity of 1α,25-dihydroxy-22-methyl-2-methylene-19-norvitamin D3.

Six new analogues of 1α,25-dihydroxy-19-norvitamin D(3) (3a-4b, 5, and 6) were prepared by a convergent synthesis applying the Wittig-Horner reaction as a key step. The influence of methyl groups at C-22 on their biological activity was examined. It was established that both in vitro and in vivo activity is strongly dependent on the configuration of the stereogenic centers at C-20 and C-22.

Vitamin A in reproduction and development.

The requirement for vitamin A in reproduction was first recognized in the early 1900's, and its importance in the eyes of developing embryos was realized shortly after. A greater understanding of the large number of developmental processes that require vitamin A emerged first from nutritional deficiency studies in rat embryos, and later from genetic studies in mice. It is now generally believed that all-trans retinoic acid (RA) is the form of vitamin A that supports both male and female reproduction as well as embryonic development.

Synthesis and biological activities of vitamin D-like inhibitors of CYP24 hydroxylase.

Selective inhibitors of CYP24A1 represent an important synthetic target in a search for novel vitamin D compounds of therapeutic value. In the present work, we show the synthesis and biological properties of two novel side chain modified 2-methylene-19-nor-1,25(OH)(2)D(3) analogs, the 22-imidazole-1-yl derivative 2 (VIMI) and the 25-N-cyclopropylamine compound 3 (CPA1), which were efficiently prepared in convergent syntheses utilizing the Lythgoe type Horner-Wittig olefination reaction. When tested in a cell-free assay, both compounds were found to be potent competitive inhibitors of CYP24A1, with the cyclopropylamine analog 3 exhibiting an 80-1 selective inhibition of CYP24A1 over CYP27B1.

The all-trans retinoic acid (atRA)-regulated gene Calmin (Clmn) regulates cell cycle exit and neurite outgrowth in murine neuroblastoma (Neuro2a) cells.

The vitamin A metabolite all-trans retinoic acid (atRA) functions in nervous system development and regulates cell proliferation and differentiation. Neuroblastoma cells (SH-SY5Y and Neuro2a or N2A) exposed to atRA undergo growth inhibition and neuronal differentiation, both of which are preceded by an increase in Clmn mRNA. Treatment of N2A cells with atRA produces a reduction in phosphohistone 3 immunostaining and BrdU incorporation, both indicators of a reduction in cell proliferation.

4-Hydroxybenzyl modification of the highly teratogenic retinoid, 4-[(1E)-2-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-2-naphthalenyl)-1-propen-1-yl]benzoic acid (TTNPB), yields a compound that induces apoptosis in breast cancer cells and shows reduced teratogenicity.

Retinoids are a class of compounds with structural similarity to vitamin A. These compounds inhibit the proliferation of many cancer cell lines but have had limited medical application as they are often toxic at therapeutic levels. Efforts to synthesize retinoids with a greater therapeutic index have met with limited success.

Nav2 hypomorphic mutant mice are ataxic and exhibit abnormalities in cerebellar development.

Development of the cerebellum involves a coordinated program of neuronal process outgrowth and migration resulting in a foliated structure that plays a key role in motor function. Neuron navigator 2 (Nav2) is a cytoskeletal-interacting protein that functions in neurite outgrowth and axonal elongation. Herein we show that hypomorphic mutant mice lacking the full-length Nav2 transcript exhibit ataxia and defects in cerebellar development.

Removal of the 26-methyl group from 19-nor-1α,25-dihydroxyvitamin D₃ markedly reduces in vivo calcemic activity without altering in vitro VDR binding, HL-60 cell differentiation, and transcription.

Twelve new analogues of 19-nor-1α,25-dihydroxyvitamin D₃ (5-16) were prepared by convergent syntheses, employing the Wittig-Horner reaction. The necessary Grundmann type ketones (45-48), possessing fixed configurations of the hydroxyl group at C-25, were obtained by a multistep procedure from commercial vitamin D₂ and enantiomers of 1,3-butanediol (23 and 24). We have examined the influence of removal of one of the methyl groups located at C-25 on the biological in vitro and in vivo activity.

The vitamin D analogue 2MD increases bone turnover but not BMD in postmenopausal women with osteopenia: results of a 1-year phase 2 double-blind, placebo-controlled, randomized clinical trial.

Most osteoporosis drugs act by inhibiting bone resorption. A need exists for osteoporosis therapies that stimulate new bone formation. 2-Methylene-19-nor-(20S)-1α,25-dihydroxyvitamin D(3) (2MD) is a vitamin D analogue that potently stimulates bone formation activity in vitro and in the ovariectomized rat model.

Vitamin A deficiency results in meiotic failure and accumulation of undifferentiated spermatogonia in prepubertal mouse testis.

Vitamin A (retinol) is required for maintenance of adult mammalian spermatogenesis. In adult rodents, vitamin A withdrawal is followed by a loss of differentiated germ cells within the seminiferous epithelium and disrupted spermatogenesis that can be restored by vitamin A replacement. However, whether vitamin A plays a role in the differentiation and meiotic initiation of germ cells during the first round of mouse spermatogenesis is unknown.

Identification of a unique subset of 2-methylene-19-nor analogs of vitamin D with comedolytic activity in the rhino mouse.

The active metabolite of vitamin D, 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), and a series of 2-methylene-19-nor analogs of 1,25(OH)(2)D(3) were evaluated for their ability to reduce the size of utricles (comedolytic activity) in a rhino mouse model of acne. All analogs tested, as well as the native hormone, increased the skin epidermal thickness. In contrast, only a subset of analogs that lacked a full side chain and 25-hydroxyl group were found to possess comedolytic activity.