Profil d'expression des fibroblastes de souris embryonnaires avec une suppression dans le domaine hélicase de l'homologue du gène Werner traité avec du peroxyde d'hydrogène

Le syndrome de Werner (SW) est une maladie génétique de transmission autosomique récessive qui cause le vieillissement prématuré. La maladie est causée par une mutation dans le gène Werner (WRN). Étant donné que le niveau d'espèces réactives d'oxygène (EROs) est élevé chez les personnes atteintes du SW et que c'est probablement un facteur causant une partie du phénotype, nous avons vérifié le phénomène au niveau cellulaire. Pour ce faire, nous avons analysé des fibroblastes de souris embryonnaires (FSEs) de type sauvage (TS) et des FSEs ayant une deletion dans une partie du domaine hélicase de la protéine homologue de WRN (Wrn[delta]hel/[delta]hel). Nous avons mesuré le niveau d'EROs dans ces cellules. Après avoir constaté que le niveau d'EROs est plus élevé dans les FSEs Wrn[delta]hel/[delta]hel que dans les FSEs TS, nous avons mesuré les effets directs et indirects de cette augmentation du niveau d'EROs au plan de la transcription globale dans ces cellules. Finalement, pour mieux comprendre l'impact des EROs dans le phénotype, nous avons étudié l'effet de l'addition d'EROs exogènes sur les cellules en culture. Nous avons donc traité des FSEs TS et Wm mutants avec du peroxyde d'hydrogène. À l'aide de biopuces à ADN, nous avons comparé le profil d'expression génique des FSEs traités au peroxyde d'hydrogène par rapport aux cellules non traitées. Nous avons par la suite validé les résultats des biopuces à ADN par transcriptase inverse suivi d'une réaction de polymerase en chaîne quantitative (TI-RPC) et analysé les données avec le programme PANTHER (Protein ANalysis THrough Evolutionary Relationships). Les EROs exogènes ont peu d'impact sur le profil d'expression des gènes chez les FSEs Wrn mutants en comparaison avec les FSEs TS car ces cellules démontrent déjà un niveau d'EROs plus élevé que la normale. Toutefois, plusieurs sentiers biologiques déjà affectés chez les FSEs Wrn mutants ont été affectés de la même façon dans les FSEs TS traités au peroxyde d'hydrogène. D'ailleurs, plusieurs de ces sentiers biologiques sont étroitement reliés au phénotype observé chez notre modèle de souris Wrn mutantes ainsi que chez les patients atteints du SW

The Evolution of the Fractions of Quiescent and Star-forming Galaxies as a Function of Stellar Mass Since z=3: Increasing Importance of Massive, Dusty Star-forming Galaxies in the Early Universe

Using the UltraVISTA DR1 and 3D-HST catalogs, we construct a stellar-mass-complete sample, unique for its combination of surveyed volume and depth, to study the evolution of the fractions of quiescent galaxies, moderately unobscured star-forming galaxies, and dusty star-forming galaxies as a function of stellar mass over the redshift interval $0.2 \le z \le 3.0$. We show that the role of dusty star-forming galaxies within the overall galaxy population becomes more important with increasing stellar mass, and grows rapidly with increasing redshift. Specifically, dusty star-forming galaxies dominate the galaxy population with $\log{(M_{\rm star}/M_{\odot})} \gtrsim 10.3$ at $z\gtrsim2$. The ratio of dusty and non-dusty star-forming galaxies as a function of stellar mass changes little with redshift. Dusty star-forming galaxies dominate the star-forming population at $\log{(M_{\rm star}/M_{\odot})} \gtrsim 10.0-10.5$, being a factor of $\sim$3-5 more common, while unobscured star-forming galaxies dominate at $\log{(M_{\rm star}/M_{\odot})} \lesssim 10$. At $\log{(M_{\rm star}/M_{\odot})} > 10.5$, red galaxies dominate the galaxy population at all redshift $z<3$, either because they are quiescent (at late times) or dusty star-forming (in the early universe).Comment: 7 pages, 4 figures, 1 table. Accepted by Astrophysical Journal Letters after minor revisio

The rest-frame optical (900nm) galaxy luminosity function at z ~ 4-7: abundance matching points to limited evolution in the M_(STAR)/M_(HALO) ratio at z ⩾ 4

We present the first determination of the galaxy luminosity function (LF) at z ~ 4, 5, 6, and 7, in the rest-frame optical at λ_(res) ~ 900 nm (z' band). The rest-frame optical light traces the content in low-mass evolved stars (~stellar mass—M*), minimizing potential measurement biases for M*. Moreover, it is less affected by nebular line emission contamination and dust attenuation, is independent of stellar population models, and can be probed up to z ~ 8 through Spitzer/IRAC. Our analysis leverages the unique full-depth Spitzer/IRAC 3.6–8.0 μm data over the CANDELS/GOODS-N, CANDELS/GOODS-S, and COSMOS/UltraVISTA fields. We find that, at absolute magnitudes where M_z’ is fainter than ≳-23 mag, M_z’ linearly correlates with M_(UV, 1600). At brighter M_z’, M_(UV, 1600) presents a turnover, suggesting that the stellar mass-to-light ratio M*/L_(UV, 1600) could be characterized by a very broad range of values at high stellar masses. Median-stacking analyses recover an M*/L_z’ roughly independent on M_z’ for M_z’ ≳ -23 mag, but exponentially increasing at brighter magnitudes. We find that the evolution of the LF marginally prefers a pure luminosity evolution over a pure density evolution, with the characteristic luminosity decreasing by a factor of _5x between z ~ 4 and z ~ 7. Direct application of the recovered M*/L_z’ generates stellar mass functions consistent with average measurements from the literature. Measurements of the stellar-to-halo mass ratio at fixed cumulative number density show that it is roughly constant with redshift for M_h ≳ 10^(12) M⊙. This is also supported by the fact that the evolution of the LF at 4 ≾ z ≾ 7 can be accounted for by a rigid displacement in luminosity, corresponding to the evolution of the halo mass from abundance matching

How Massive are Massive Compact Galaxies?

Using a sample of nine massive compact galaxies at z ~ 2.3 with rest-frame optical spectroscopy and comprehensive U through 8um photometry we investigate how assumptions in SED modeling change the stellar mass estimates of these galaxies, and how this affects our interpretation of their size evolution. The SEDs are fit to Tau-models with a range of metallicities, dust laws, as well as different stellar population synthesis codes. These models indicate masses equal to, or slightly smaller than our default masses. The maximum difference is 0.16 dex for each parameter considered, and only 0.18 dex for the most extreme combination of parameters. Two-component populations with a maximally old stellar population superposed with a young component provide reasonable fits to these SEDs using the models of Bruzual & Charlot (2003); however, using models with updated treatment of TP-AGB stars the fits are poorer. The two-component models predict masses that are 0.08 to 0.22 dex larger than the Tau-models. We also test the effect of a bottom-light IMF and find that it would reduce the masses of these galaxies by 0.3 dex. Considering the range of allowable masses from the Tau-models, two-component fits, and IMF, we conclude that on average these galaxies lie below the mass-size relation of galaxies in the local universe by a factor of 3-9, depending on the SED models used.Comment: 5 pages, 2 figures, accepted for publication in ApJ Letter

The Age Spread of Quiescent Galaxies with the NEWFIRM Medium-band Survey: Identification of the Oldest Galaxies out to z~2

With a complete, mass-selected sample of quiescent galaxies from the NEWFIRM Medium-Band Survey (NMBS), we study the stellar populations of the oldest and most massive galaxies (>10^11 Msun) to high redshift. The sample includes 570 quiescent galaxies selected based on their extinction-corrected U-V colors out to z=2.2, with accurate photometric redshifts, sigma_z/(1+z)~2%, and rest-frame colors, sigma_U-V~0.06 mag. We measure an increase in the intrinsic scatter of the rest-frame U-V colors of quiescent galaxies with redshift. This scatter in color arises from the spread in ages of the quiescent galaxies, where we see both relatively quiescent red, old galaxies and quiescent blue, younger galaxies towards higher redshift. The trends between color and age are consistent with the observed composite rest-frame spectral energy distributions (SEDs) of these galaxies. The composite SEDs of the reddest and bluest quiescent galaxies are fundamentally different, with remarkably well-defined 4000A- and Balmer-breaks, respectively. Some of the quiescent galaxies may be up to 4 times older than the average age- and up to the age of the universe, if the assumption of solar metallicity is correct. By matching the scatter predicted by models that include growth of the red sequence by the transformation of blue galaxies to the observed intrinsic scatter, the data indicate that most early-type galaxies formed their stars at high redshift with a burst of star formation prior to migrating to the red sequence. The observed U-V color evolution with redshift is weaker than passive evolution predicts; possible mechanisms to slow the color evolution include increasing amounts of dust in quiescent galaxies towards higher redshift, red mergers at z<1, and a frosting of relatively young stars from star formation at later times.Comment: 20 pages, 20 figures, accepted for publication in Ap

Control of somatic embryogenesis and embryo development by AP2 transcription factors

Members of the AP2 family of transcription factors, such as BABY BOOM (BBM), play important roles in cell proliferation and embryogenesis in Arabidopsis thaliana (AtBBM) and Brassica napus (BnBBM) but how this occurs is not understood. We have isolated three AP2 genes (GmBBM1, GmAIL5, GmPLT2) from somatic embryo cultures of soybean, Glycine max (L.) Merr, and discovered GmBBM1 to be homologous to AtBBM and BnBBM. GmAIL5 and GmPLT2 were homologous to Arabidopsis AINTEGUMENTA-like5 (AIL5) and PLETHORA2 (PLT2), respectively. Constitutive expression of GmBBM1 in Arabidopsis induced somatic embryos on vegetative organs and other pleiotropic effects on post-germinative vegetative organ development. Sequence comparisons of BBM orthologues revealed the presence of ten sequence motifs outside of the AP2 DNA-binding domains. One of the motifs, bbm-1, was specific to the BBM-like genes. Deletion and domain swap analyses revealed that bbm-1 was important for somatic embryogenesis and acted cooperatively with at least one other motif, euANT2, in the regulation of somatic embryogenesis and embryo development in transgenic Arabidopsis. The results provide new insights into the mechanisms by which BBM governs embryogenesis

Stellar and Dust Properties of a Complete Sample of Massive Dusty Galaxies at 1≤z≤41 \le z \le 4 from MAGPHYS Modeling of UltraVISTA DR3 and Herschel Photometry

We investigate the stellar and dust properties of massive (log$(M_*/M_\odot) \ge 10.5$) and dusty ($A_V \ge 1$) galaxies at $1 \le z \le 4$ by modeling their spectral energy distributions (SEDs) obtained from the combination of UltraVISTA DR3 photometry and \textit{Herschel} PACS-SPIRE data using MAGPHYS. Although the rest-frame U-V vs V-J (UVJ) diagram traces well the star-formation rates (SFR) and dust obscuration (A$_V$) out to $z \sim 3$, $\sim$15-20\% of the sample surprisingly resides in the quiescent region of the UVJ diagram, while $\sim50$\% at $3<z<4$ fall in the unobscured star-forming region. The median SED of massive dusty galaxies exhibits weaker MIR and UV emission, and redder UV slopes with increasing cosmic time. The IR emission for our sample has a significant contribution ($>20\%$) from dust heated by evolved stellar populations rather than star formation, demonstrating the need for panchromatic SED modeling. The local relation between dust mass and SFR is followed only by a sub-sample with cooler dust temperatures, while warmer objects have reduced dust masses at a given SFR. Most star-forming galaxies in our sample do not follow local IRX-$\beta$ relations, though IRX does strongly correlate with A$_V$. Our sample follows local relations, albeit with large scatter, between ISM diagnostics and sSFR. We show that FIR-detected sources represent the extreme of a continuous population of dusty galaxies rather than a fundamentally different population. Finally, using commonly adopted relations to derive SFRs from the combination of the rest-frame UV and the observed 24$\mu$m is found to overestimate the SFR by a factor of 3-5 for the galaxies in our sample.Comment: Accpeted for publication in Ap

HFF-DeepSpace photometric catalogs of the 12 Hubble frontier fields, clusters, and parallels : photometry, photometric redshifts, and stellar masses

We present Hubble multi-wavelength photometric catalogs, including (up to) 17 filters with the Advanced Camera for Surveys and Wide Field Camera 3 from the ultra-violet to near-infrared for the Hubble Frontier Fields and associated parallels. We have constructed homogeneous photometric catalogs for all six clusters and their parallels. To further expand these data catalogs, we have added ultra-deep KS-band imaging at 2.2. mu m from the Very Large Telescope HAWK-I and Keck-I MOSFIRE instruments. We also add post-cryogenic Spitzer imaging at 3.6 and 4.5. mu m with the Infrared Array Camera (IRAC), as well as archival IRAC 5.8 and 8.0. mu m imaging when available. We introduce the public release of the multi-wavelength (0.2-8 mu m) photometric catalogs, and we describe the unique steps applied for the construction of these catalogs. Particular emphasis is given to the source detection band, the contamination of light from the bright cluster galaxies (bCGs), and intra-cluster light (ICL). In addition to the photometric catalogs, we provide catalogs of photometric redshifts and stellar population properties. Furthermore, this includes all the images used in the construction of the catalogs, including the combined models of bCGs and ICL, the residual images, segmentation maps, and more. These catalogs are a robust data set of the Hubble Frontier Fields and will be an important aid in designing future surveys, as well as planning follow-up programs with current and future observatories to answer key questions remaining about first light, reionization, the assembly of galaxies, and many more topics, most notably by identifying high-redshift sources to target

Beyond UVJ: Color Selection of Galaxies in the JWST Era

We present a new rest-frame color-color selection method using "synthetic $u_s-g_s$ and $g_s-i_s$'', $(ugi)_s$ colors to identify star-forming and quiescent galaxies. Our method is similar to the widely-used $U-V$ versus $V-J$ ($UVJ$) diagram. However, $UVJ$ suffers known systematics. Spectroscopic campaigns have shown that $UVJ$-selected quiescent samples at $z \gtrsim 3$ include $\sim 10-30\%$ contamination from galaxies with dust-obscured star formation and strong emission lines. Moreover, at $z>3$, $UVJ$ colors are extrapolated because the rest-frame J-band shifts beyond the coverage of the deepest bandpasses at $< 5~\mu m$ (typically $Spitzer$/IRAC 4.5 $\mu m$ or future $JWST$/NIRCam observations). We demonstrate that $(ugi)_s$ offers improvements to $UVJ$ at $z>3$, and can be applied to galaxies in the $JWST$ era. We apply $(ugi)_s$ selection to galaxies at $0.5<z<6$ from the (observed) 3D-HST and UltraVISTA catalogs, and to the (simulated) JAGUAR catalogs. We show that extrapolation can affect $(V-J)_0$ color by up to 1 magnitude, but changes $(u_s-i_s)_0$ color by $\leq$ 0.2 mag, even at $z\simeq 6$. While $(ugi)_s$-selected quiescent samples are comparable to $UVJ$ in completeness (both achieve $\sim$85-90% at $z=3-3.5$), $(ugi)_s$ reduces contamination in quiescent samples by nearly a factor of two, from $\simeq$35% to $\simeq$17% at $z=3$, and from $\simeq$60% to $\simeq$33% at $z=6$. This leads to improvements in the true-to-false-positive ratio (TP/FP), where we find TP/FP $\gtrsim$ 2.2 for $(ugi)_s$ at $z \simeq 3.5 - 6$, compared to TP/FP $<$ 1 for $UVJ$-selected samples. This indicates that contaminants will outnumber true quiescent galaxies in $UVJ$ at these redshifts, while $(ugi)_s$ will provide higher-fidelity samples.Comment: Submitted to Ap