Influence of FOX genes on aging and aging-associated diseases. Elena Tschumak

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      FOXP2 regulates the expression of many genes during embryonic development as well as the WNT and Notch signalling pathways. Further interactions have been observed with some histone family members (H2AFX; H3f3B) and two heat shock proteins (Hsp25; Hsp90a).

      Importance of FOXP1/2/4 interaction for oncological processes Several FOXP genes have been observed in many aging relevant oncological processes. Foxp1 / 2/4-NuRD interaction is processed by the p66beta, a transcriptional repressor and a component of NuRD. During this process, the chromatin-remodelling complex regulates gene expression. He also influences the Interleukin-6. Interleukin-6 in turn contributes to the epithelial injury response and activates „myeloid cells“. The „myeloid cells“ are generally associated with cancer and stimulate eg. intestinal cells to divide, which leads to colorectal carcinoma. Artavanis-Tsakonas et al. (1999) studied NCOR2 and SNW1 as part of notch-mediated signalling and its role in proliferation and differentiation processes as well as in apoptosis. The NCOR2 is not only a FOXP2 downstream target but also shows interaction with FOXP1 during myocardial development. (Jepsen et al., 2008), (Wilke et al., 2012) NCOR2-mediated regulation can be considered as a common mechanism by which FOXP1 and other members of the FOXP family regulate gene expression during organogenesis. This study showed different effects of six FOXP1 / 2/4 protein combinations on the NCOR2. The FOXP1 / 2 combination showed the strongest effect. All combinations except the FOXP1 / 4 dimer led to increased NCOR2 expression. The FOXP2 homodimers induced decreased SNW1 expression while the FOXP1 and FOXP4 homodimers led to increased expression. The influence of FOXP1 / 2 and FOXP4 / 2 on SNW1 expression seems to be unlikely. These results gave an interesting insight into the dual FOXP2 function both as a repressor and as an activator. This ability for build different dimer-combinations may be a hint to fine-tune cell-specific transcriptional regulation. The FOXP1 / 2/4 dimer combinations are preferred. These results suggest that relative levels of FOXP1 / 2/4 proteins determine FOXP2's ability to act as an activator or repressor. The researchers found also that FOXP1 / 2, FOXP1 / 4 and FOXP2 / 4 are co-localized.

      FOXP2 modulation by alternative splicing The FOXP is also regulated by alternative splicing. This way the FoxP2 gets different isoforms and is homodimerized and this leads to a change of its activity. (Santos et al., 2011) Similar results were reported by Chen et al. (2014) and Olias et al. (2013). This FOXP2 modification was observed in the lower and dorsal thalamus, in the striatum (except Area X) and in the cerebellar Purkinje cells. These are brain areas where the FoxP2 is permanent strongly expressed. (Takahashi et al., 2003), (Ferland et al., 2003), (Haesler et al., 2004) Epigenetic FOXP2 Regulation by Methylation FOXP2 methylation plays an important role by adipositas. Spaeth et al. showed in „The FOXP1, FOXP2 and FOXP4 transcription factors are required for islet alpha cell proliferation and function in mice“ (2015) that Foxp2 is important for the growth and function of pancreatic alfa islands. The islets of Langerhans of the exocrine pancreas contain five different cell populations: the beta, the alpha, the delta, the epsilon and the pancreatic polypeptide cells. These secrete the ghrelin and pancreatic polypeptide hormones (insulin, glucagon, somatostatin). The authors noted that interaction between FOXP2 and FOXP1 / FOXP4 is required for alpha-islet cell proliferation of the mice. Adult beta cells normally secrete insulin, the alpha cells - the glucagon. Autoimmune beta-cell destruction causes type 1 diabetes while type 2 diabetes is characterized by insulin resistance in the peripheral tissues. Type 2 diabetes is accompanied by insulin deficiency and the loss of beta cell identity. The transcription factors accomplish the reprogramming of terminally differentiated cells and embryonic stem cells into the beta-like cells. The members of the FOX superfamily play crucial roles in these processes, which is also aging relevant. E.g., FOXA2 is known as a pancreatic cell fate regulator. FOXM1 controls expression of cycle factors and increases beta cell mass during metabolic stress, including pregnancy stress and partial pancreatectomy. Metformin, Berberine, EGCG, quercetin and other natural products activate cancer relevant AMPK and decrease mTORC1 activity. MTORC1 activity is frequently elevated in CSC including pancreatic CSCs (Ming et al., 2014; Rozengurt et al., 2014; Matsubara et al., 2013) EGCG also positively effects cancer and aging relevant p21Cip1 and negatively the PI3K/PTEN/Akt/mTORC1 pathway (Chen et al., 2012)

      According to Alessandro et al., (2015) MET positively influences decreased mitochondrial transmembrane potential, sensitivity to TRAIL via DR5-upregulation, ROS-level and cell cycle in cancer via miR-221 (Tanaka et al., 2015 Matsubara et al., 2013) but also via TRAIL interaction. In this case G-Phase arrest happens via p27Kip-1 and via interaction between caspases (Coleman et al., 2013) Other plant-derived cancer relevant chemicals are e.g. SHH pathway regulating catechins cyclopamine, norcantharidin, sulforaphane and zerumbone (Huang et al., 2013) They act best in combination and suppress ALDH1, MMP-2 and MMP-9 via KRAS under- and let7 miR- upregulation. (Appari et al., 2014) Momordica charantia has positive effect on inflammation and on cancer (Dandawate et al.,2016), e.g. on ovarian cancer via of AMPK up-, mTOR/p70S6K and AKT/ERK/FOXM1 signalling cascade underregulation (Yung et al., 2016) possibly via Alpha-Momorcharin (Deng et al., 2014).

      Also Rooperol influences apoptosis with the help of mitochondrial membrane potential. It upregulates ROS via TP53 activation, but also OCT4 and stemness relevant SOX2 and NANOG (Ali et al., 2015) It also increases Pomiferin level, which influences BIM1 and NESTIN (Zhao et al., 2013)

      FOXP1, FOXP2 and FOXP4 are of great importance for alpha cell proliferation and function and are expressed in the pancreas and eyes of Xenopus laevis during its development. FOXA1 and FOXA2 also regulate glucagon production and secretion-controlling genes: the MAFB, the Brn4 (also known as the Pou3f4), the PCK2, the Nkx2-2, the Kir6.1 (also known as the Kcnj8), the Sur1 (also known as the ABCC8) and the GIPR.

      FOXP2 regulation by external factors Regulation by PH level Blane and Fanucchi (2015) studied in "Effect of pH on the Structure and DNA Binding of the FOXP2 Forkhead Domain." effects of pH from changes 5 to 9 on FOXP2 function and reported that a change in pH (pH 7.5) directly affects the FOXP2 binding affinity via the altered hydrogen bonding pattern. This is due to the protonation or deprotonation of His554 (the amino group of its imidazole side chain, pKa ~ 6.5). The researchers used as methods gel permeation chromatography, ultraviolet circular dichroism, intrinsic and extrinsic fluorescence etc. Their results showed that the pH does not affect the protein secondary structure in the presence or absence of DNA but alters its tertiary structure. The protein showed a less compact structure at low pH in the absence of DNA. When the DNA was added, the protein became more compact, even at low pH and its dimerization potential increased. They regarded the pH as a regulatory mechanism of FOXP2 forkhead domain (FHD) transcription that interacts with the DNA by helix placement in the major groove. These results could also be important in cancer tissue, where FOXP2 expression plays an important role. E.g., not only the genetic component but also a previous chronic gastric ulcer with changed pH plays a significant role in gastric cancer. The gastric ulcer-causing Helicobacter pylori gains an almost pH-neutral environment with the help of the enzyme urease, which splits the urea into carbon dioxide and ammonia. It would be of great scientific interest to investigate whether the change in the gastric pH together with FOXP2 have an effect on the development of gastric cancer.

       Regulation through Vitamin-D

      Hawes et al. (2015) showed in „Maternal vitamin D deficiency age foetal brain development in the BALB / c mouse“ how the maternal vitamin D deficiency alters foetal brain development in transgenic Balb / c mice. Before and during pregnancy a vitamin D-rich (2.195 IU / kg) or a low (0 IU / kg) diet was given for 5 weeks and the foetal brains were analysed morphologically and for gene expression at 14.5 or 17.5. embryonic day. It was found that the vitamin D deficiency during pregnancy leads to reduction of rump length, lateral ventricle volume and head size. The FoxP2 expression and at the same time the expression of Brain-Derived Neurotrophic Factor (BDNF), the Transforming growth factor-β1 (TGF-β1) and brain tyrosine hydroxylase (TH) in dopaminergic neurons was altered. The vitamin D-poor diet reduced FOXP2 expression in immunoreactive cells and in the developing cortex in female foetuses. These results allowed deeper insight into the medically relevant reasons for foetal degeneration accompanied by prenatal