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Review
. 2022;162(8-9):405-528.
doi: 10.1159/000529376. Epub 2023 Jan 30.

Fourth Report on Chicken Genes and Chromosomes 2022

Jacqueline Smith  1 , James M Alfieri  2   3   4 , Nick Anthony  5 , Peter Arensburger  6 , Giridhar N Athrey  2   4 , Jennifer Balacco  7 , Adam Balic  1 , Philippe Bardou  8 , Paul Barela  9 , Yves Bigot  10 , Heath Blackmon  2   3 , Pavel M Borodin  11 , Rachel Carroll  12 , Meya C Casono  9 , Mathieu Charles  13 , Hans Cheng  14 , Maddie Chiodi  9 , Lacey Cigan  9 , Lyndon M Coghill  15 , Richard Crooijmans  16 , Neelabja Das  9 , Sean Davey  9 , Asya Davidian  17 , Fabien Degalez  18 , Jack M Dekkers  19   20 , Martijn Derks  16 , Abigail B Diack  1 , Appolinaire Djikeng  21 , Yvonne Drechsler  22 , Alexander Dyomin  17 , Olivier Fedrigo  7 , Steven R Fiddaman  23 , Giulio Formenti  7 , Laurent A F Frantz  24   25 , Janet E Fulton  26 , Elena Gaginskaya  17 , Svetlana Galkina  17 , Rodrigo A Gallardo  19   27 , Johannes Geibel  28   29 , Almas A Gheyas  1 , Cyrill John P Godinez  30 , Ashton Goodell  9 , Jennifer A M Graves  31   32 , Darren K Griffin  33 , Bettina Haase  7 , Jian-Lin Han  34   35 , Olivier Hanotte  35   36   37 , Lindsay J Henderson  1 , Zhuo-Cheng Hou  38 , Kerstin Howe  39 , Lan Huynh  40 , Evans Ilatsia  41 , Erich D Jarvis  7 , Sarah M Johnson  9 , Jim Kaufman  40   42   43 , Terra Kelly  19   27 , Steve Kemp  44 , Colin Kern  45 , Jacob H Keroack  9 , Christophe Klopp  46 , Sandrine Lagarrigue  18 , Susan J Lamont  19   20 , Margaret Lange  47 , Anika Lanke  48 , Denis M Larkin  49 , Greger Larson  50 , John King N Layos  51 , Ophélie Lebrasseur  52   53 , Lyubov P Malinovskaya  54 , Rebecca J Martin  43 , Maria Luisa Martin Cerezo  55 , Andrew S Mason  56 , Fiona M McCarthy  9 , Michael J McGrew  1   21 , Jacquelyn Mountcastle  7 , Christine Kamidi Muhonja  41   44 , William Muir  57 , Kévin Muret  58 , Terence D Murphy  59 , Ismael Ng'ang'a  24 , Masahide Nishibori  60 , Rebecca E O'Connor  33 , Moses Ogugo  44 , Ron Okimoto  5 , Ochieng Ouko  41 , Hardip R Patel  61 , Francesco Perini  1   62 , María Ines Pigozzi  63 , Krista C Potter  9 , Peter D Price  64 , Christian Reimer  28 , Edward S Rice  65 , Nicolas Rocos  40 , Thea F Rogers  66 , Perot Saelao  19   45   67 , Jens Schauer  28 , Robert D Schnabel  68 , Valerie A Schneider  59 , Henner Simianer  29 , Adrian Smith  23 , Mark P Stevens  1 , Kyle Stiers  15 , Christian Keambou Tiambo  44 , Michele Tixier-Boichard  13 , Anna A Torgasheva  11 , Alan Tracey  39 , Clive A Tregaskes  42   43 , Lonneke Vervelde  1 , Ying Wang  19   45 , Wesley C Warren  65   68 , Paul D Waters  69 , David Webb  59 , Steffen Weigend  28   29 , Anna Wolc  20   26 , Alison E Wright  64 , Dominic Wright  55 , Zhou Wu  1 , Masahito Yamagata  70 , Chentao Yang  71 , Zhong-Tao Yin  38 , Michelle C Young  9 , Guojie Zhang  72 , Bingru Zhao  73 , Huaijun Zhou  19   45
Affiliations
Review

Fourth Report on Chicken Genes and Chromosomes 2022

Jacqueline Smith et al. Cytogenet Genome Res. 2022.
No abstract available

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Conflict of interest statement

All authors have no conflicts of interest.

The authors have no conflicts of interest to declare.

There are no conflicts of interest to declare.

The authors declare no conflicts of interest.

The authors declare no competing interests.

The authors have no conflicts of interest to declare.

There are no conflicts of interest.

The authors have no conflicts of interest to declare.

The authors have no conflicts of interest to declare.

The authors report no competing interests.

The authors declare that they have no competing interests.

The author has no conflicts of interest to declare.

The authors have no conflicts of interest to declare.

The author declares no conflict of interest.

The author declares no conflicts of interest.

The authors declare no conflicts of interest.

The authors declare that they have no conflict of interest.

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The authors of this document declare that they have no affiliations with or involvement in any organization or entity with any financial interest in the subject matter or materials discussed in this manuscript.

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Figures

Fig. 1
Fig. 1
Assembled structural errors detected in RJF compared to broiler for chromosome 27 using Hi-C mapped data to the scaffolds. Genetic linkage map markers (n= 125) displayed as green tic marks below the xaxis for the chromosome 27 heat map were mapped to each assembly to validate sequence order and orientation.
Fig. 2
Fig. 2
Sequenced differences in the phased broiler and layer genomes for macro- (a) and micro-autosomes (b). From the inside out SNV density (red), window size of 500 kb, range of 0 to 2.5%, indels <50 bp (coral), 500 kb window size and 0–0.8%; large indels (blue) per Mb, range of 0 to 60; CNV count per Mb (green); highlighted inversions (black dashes); chicken karyotype (varied color); ideograms of GRCg7b and GRCg7w chromosomes (varied colors).
Fig. 3
Fig. 3
The distribution of called heterozygous SNVs across chicken macrochromosome 7 (a) and microchromosome 20 (b) in the three assemblies. Rainfall plots of heterozygous variants depict their location, and each unique color indicates a different type of base substitution. We only include variants that passed all filters and were heterozygous in either reference source.
Fig. 4
Fig. 4
The RNAseq alignment detection of multimapping events and rRNA number and size distributions by reference source.
Fig. 5
Fig. 5
ALVE integration, propagation, and degradation within the chicken genome. a Retroviral genomic lifecycle. Retroviral positive sense, single-stranded RNA is reverse transcribed into cDNA and associates with the retroviral integrase integration complex, which primes the cDNA 3′ ends and initiates strand transfer with genomic DNA. Integration creates overhangs which are repaired by host machinery, creating target site duplications (TSDs; grey). Following integration, retroviral expression and retrotransposition is possible. Over evolutionary timescales integrated ERVs degrade, either by nonhomologous recombination events (I, II) or internal LTR recombination leaving solo LTRs (III). b Schematic indicates an intact ALVE with putative transcripts, with the ribosomal −1 frame slip and recognition site for miR-155 indicated. Phased chicken genome ALVE content and integrity is shown, with likely transcript and regulatory implications. CA, capsid; INT, integrase; LTR, long terminal repeat; MA, matrix; NC, nucleocapsid; PR, protease; RH, RNaseH; RT, reverse transcriptase; SU, surface; TM, transmembrane.
Fig. 6
Fig. 6
Evolution of major groups of reptiles (including birds) with major extinction events noted. Timelines given but scale is not linear.
Fig. 7
Fig. 7
Chromosome evolution from the diapsid ancestor, to the archelosaur ancestor, via the theropod dinosaur lineage, to modern birds and finally to chicken. A recognisable avian pattern had evolved just before the dinosaurs emerged 240 million years ago. After this time, chromosome inversions were the principal mechanisms of change. a 275 million years ago. b 255 million years ago. c 240 million years ago at the dawn of the dinosaurs. d Snapshot 100–150 years ago. e Modern chicken.
Fig. 8
Fig. 8
Imagined dinosaur karyotype (deliberately manipulated image based on chicken and spiny soft-shelled turtle chromosomes).
Fig. 9
Fig. 9
Bird whole-genome alignments. a Alignment of chicken to zebra finch [Rhie et al., 2021], Anna's hummingbird [Rhie et al., 2021], superb fairywren [Penalba et al., 2020], and the ancestral emu genome [Liu J et al., 2021]. b Alignment of the chicken genome to species that have undergone significant chromosome rearrangement: saker falcon, California condor [Robinson et al., 2021], and golden eagle [Mead et al., 2021]. Macrochromosomes are green, microchromosmes purple, and Z chromosomes orange. Green ribbons show macro-to-macro homologies, purple show micro-to-micro homologies, blue show macro-to-micro homologies, and grey show Z-to-Z homologies.
Fig. 10
Fig. 10
Different mechanisms of lncRNA roles. Effects at the nuclear and telomere (A, B), transcriptional (C, D), post-transcriptional (E–H), translational (I), and post-translational levels (J–L). Role as small ORF host (M) and small noncoding RNA host (N). Implication in the exosome-mediated transfer (O). In purple, lncRNA; in blue, DNA; in green, other RNAs; in dark red, proteins. For more examples, other genes are presented in Muret et al. [2019], specifically genes involved in the regulation of lipid metabolism and their regulatory mechanisms.
Fig. 11
Fig. 11
Assembly versions associated with the chicken genome (a) and the number of publications associated with them (b). a RJF, Red Jungle fowl; W–L, White Leghorn; Cov., coverage; Scaf, scaffold; N50, scaffold N50. For more details, see online supplementary Material 5, Table 1. b Blue numbers, articles published using the corresponding assembly during the year 2020. Identification was made on PubMed Central by searching for the assembly name in different formats (e.g., GRCg6a or GRCg6 or Galgal6).
Fig. 12
Fig. 12
Gene numbers provided by NCBI's RefSeq and EMBL-EBI's Ensembl according to the genome annotation and genome assembly versions (a) and transcript model changes between two genome annotation versions from NCBI RefSeq for the same assembly − GRCg7b (b). a PCG, protein-coding gene; lncRNA: long noncoding RNA. b Comparison between versions 105 and 106 provided by NCBI [NCBI RefSeq, 2022]. Briefly, a score (between 0 and 1) for current and previous transcript features is calculated based on overlap in exon sequence and matches in exon boundaries. Pairs of current and previous features were categorized based on these scores and considering changes in attributes. New, new transcript models; Deprecated, transcripts removed or merged in the new version; Major changes, changes with great impact on the sequence or on the transcript attributes; Minor changes, minimal change ensuring similarity.
Fig. 13
Fig. 13
Features of the current NCBI RefSeq (v106) and EMBL-EBI Ensembl (v107) genome annotations based on the latest GRCg7b genome assembly. a Number of genes and transcripts according to gene biotypes for the two genome annotations. b The transcript models were compared between the two annotations according to 4 main classes (Equal isoform, New isoform, New loci, and Artifacts) according to the software “GffCompare” (options: -S --no-merge) [Pertea and Pertea, 2020]. c #Tr/gn, number of transcripts per gene; #Ex/tr, number of exons per transcript; Tr. Size, transcript size considering only exonic regions; Ex. Size, exon size; In. Size, intron size. The median transcript sizes between RefSeq and Ensembl are 3,465 bp versus 2,317 bp, respectively, p< 10−16 (Wilcoxon rank sum test); for PCG 3,634 bp versus 2,870 bp, * p< 10−16; for lncRNAs 2,952 bp versus 1,487 bp, *p< 10−16.
Fig. 14
Fig. 14
Numbers of differentially expressed genes identified between genetic lines. A false discovery rate <0.05 was used to classify genes as differentially expressed. AH, acute heat stress; CH, chronic heat stress and NDV infection at 2 dpi; FCLC, Fayoumi non-treated versus Leghorn non-treated; FTLT, Fayoumi treated versus Leghorn treated.
Fig. 15
Fig. 15
Numbers of differentially expressed genes identified within genetic lines. A false discovery rate <0.05 was used to classify genes as differentially expressed. AH, acute heat stress; CH, chronic heat stress and NDV infection at 2 dpi; LTLC, Leghorn treated versus non-treated; FTFC, Fayoumi treated versus non-treated.
Fig. 16
Fig. 16
Venn diagram of differentially expressed genes within genetic lines in the hypothalamus. LTLCAH, Leghorn treated versus non-treated with acute heat stress; FTFCAH, Fayoumi treated versus non-treated with acute heat stress; LTLCCH&NDV, Leghorn treated versus non-treated with chronic heat stress and 2 dpi NDV infection; FTFCCH&NDV, Fayoumi treated versus non-treated with chronic heat stress and 2 dpi NDV infection.
Fig. 17
Fig. 17
Venn diagram of differentially expressed genes within genetic lines in the breast muscle. LTLCAH, Leghorn treated versus non-treated with acute heat stress; FTFCAH, Fayoumi treated versus non-treated with acute heat stress; LTLCCH&NDV, Leghorn treated versus non-treated with chronic heat stress and 2 dpi NDV infection; FTFCCH&NDV, Fayoumi treated versus non-treated with chronic heat stress and 2 dpi NDV infection.
Fig. 18
Fig. 18
Gene ontology (GO) biological processes and KEGG pathway overrepresentation (p< 0.05 and FDR <20%) for within-line comparisons in the hypothalamus. a GO terms and KEGG pathways significantly enriched by upregulated genes in the LTLCAH comparison. b GO terms and KEGG pathways significantly enriched by downregulated genes in the LTLCAH comparison. c GO terms and KEGG pathways significantly enriched by downregulated genes in the LTLCCH comparison. d GO terms and KEGG pathways significantly enriched by upregulated genes in the FTFCAH comparison. e GO terms and KEGG pathways significantly enriched by downregulated genes in the FTFCAH comparison. f GO terms and KEGG pathways significantly enriched by upregulated genes in the FT­FCCH comparison. g GO terms and KEGG pathways significantly enriched by downregulated genes in the FTFCCH comparison.
Fig. 19
Fig. 19
Gene ontology (GO) biological processes and KEGG pathway overrepresentation (p< 0.05 and FDR <20%) for within-line comparisons in the breast muscle. a GO terms and KEGG pathways significantly enriched by upregulated genes in the LTLCAH comparison. b GO terms and KEGG pathways significantly enriched by downregulated genes in the LTLCAH comparison. c GO terms and KEGG pathways significantly enriched by upregulated genes in the FTFCAH comparison. d GO terms and KEGG pathways significantly enriched by upregulated genes in the LTLCCH comparison. e GO terms and KEGG pathways significantly enriched by downregulated genes in the LTLCCH comparison. f GO terms and KEGG pathways significantly enriched by upregulated genes in the FTFCCH comparison. g GO terms and KEGG pathways significantly enriched by downregulated genes in the FT­FCCH comparison.
Fig. 20
Fig. 20
Comparative analysis of significantly enriched canonical pathways through Ingenuity Pathway Analysis among differentially expressed genes by genetic line and treatment in the breast muscle (p< 0.05 and z>|1.64|), where orange (positive z-score) refers to predicted activation and blue (negative z-score) to predicted inhibition.
Fig. 21
Fig. 21
Module-trait relationships from WGCNA. Each module (yaxis) is correlated with each phenotype (xaxis); the correlation and pvalues were reported for each comparison. Strong positive correlations are coloured in red, and strong negative correlations are coloured in green. TrtAH, acute heat stress; TrtCH, chronic heat stress and 2 dpi NDV infection. a Correlation coefficients. b pvalues.
Fig. 22
Fig. 22
Top GO terms and KEGG pathways enriched by genes highly expressed in the turquoise module in the breast muscle.
Fig. 23
Fig. 23
The blue module gene network. Red highlighted dots indicate immune-related genes, blue highlighted dots metabolic genes. Gray highlighted dots show all other genes in the blue module.
Fig. 24
Fig. 24
Phopholipase C signaling pathway and gene heat map in within-line comparisons in the breast muscle. a Molecule activity prediction of the pathway in Leghorn birds with CH&NDV treatment. b Molecule activity prediction of the pathway in Fayoumi birds with AH. c DEG heatmap matching the pathway.
Fig. 25
Fig. 25
Calcium signaling pathway and gene heat map in within-line comparisons in the breast muscle. a Molecule activity prediction of the pathway in Leghorn birds with CH&NDV treatment. b Molecule activity prediction of the pathway in Fayoumi birds with AH. c DEG heat map matching the pathway.
Fig. 26
Fig. 26
Sequence organization of transposable elements in avian genomes. a CR1 elements are composed of segments that resemble long retro-inserted messenger RNA (mRNA) with an A-rich tail at their 3′ end. Within a “species” of CR1s many copies are truncated at their 5′ ends. Full-length elements contain 2 open reading frames (ORFs) whith ORF2 encoding a protein containing an apurinic endonuclease domain fused to a reverse transcriptase. b SINEs using the CR1 machinery are present in some bird species, but not in chickens. They consist of the fusion of a former tRNA to a 3′ CR1 end. c LTR retrotransposons have all the signatures of an endogenous retrovirus-like element, including long terminal repeats (LTR) at both ends and ORFs coding for a group antigen (Gag), a reverse transcriptase (RT), and in some case an envelope protein (Env). d DNA transposons that transpose directly from DNA to DNA have short terminal inverted repeats (arrows) at both ends. When these elements are intact, they may contain a gene encoding a transposase, an enzyme required for their own transposition. There are also internally deleted forms such as Galluhopand chimeric elements such as Charlie/Galluhop.
Fig. 27
Fig. 27
Hybridization of GC-rich and GC-poor DNA probes on chicken chromosomes. Chicken DNA fractions characterized as having the lowest and the highest GC levels were hybridized to chicken chromosomes. a The DNA fraction with the highest GC level (red signals) was localized to the microchromosomes and to telomeric bands of the macrochromosomes (see white arrows as examples). Some internal bands of the macrochromosomes also hybridized (see yellow arrows as examples). In contrast, the DNA fraction with the lowest GC levels (green signals) localized to the internal bands of the macrochromosomes. b The same metaphase shown in the panel is DAPI stained in order to better show microchromosomes. The bar in the upper right is 5 μm long. Figure taken from Federico et al. [2005].
Fig. 28
Fig. 28
Comparison of the chicken Gallus g. domesticusand guinea fowl N. meleagrisrDNA repeat structure. The structures of chicken rDNA repeat II from the WAG137G04 BAC clone (a) and guinea fowl rDNA repeat II from the NCBI JABXER010000123 contig (b). 18S, 5.8S, and 28S rRNA genes are indicated by red blocks, external (5′ and 3′ETS) and internal (ITS1 and ITS2) transcribed spacers are indicated by yellow blocks, and intergenic transcribed spacers (IGS) by green blocks. GC pair distribution is shown in the graphs as “GC%”.
Fig. 29
Fig. 29
Chicken and guinea fowl IGS structure. a Four aligned chicken IGS sequences. IGS_I, IGS_II, and IGS_III are from the Gallus g. domesticusBAC-clone containing rDNA (WAG137G04). IGS_IV belongs to a red jungle fowl (AADN04001305.1). All four IGS have different sizes caused by the difference in repeat blocks of each type (SV-AL, EL, VAL). The unique regions are almost of the same length in all analysed IGS (see also online suppl. Material 11, Table S1). b Three aligned IGS sequences from the guinea fowl JABXER010000123 contig. Two of them are completely identical, IGS_III has an insertion at 5,500 bp (dotted rectangle). Each of the IGS contains no EL repeats, one SV-AL repeat block and at least two VAL repeat blocks, differentiated into 6 repeat variants (see also online suppl. Material 11, Fig. S1, S2, Data S1). A species-specific Nme repeat block following SV-AL block is marked in black. Sequence gaps are designated with fine black lines.
Fig. 30
Fig. 30
Internal IGS repeats demonstrate a HOR (high order repeat) organisation. Contracted IGS_II figure from WAG137G04 contig of G. g. domesticus(a) and IGS_I figure from JABXER010000123 contig of N. meleagris(b).
Fig. 31
Fig. 31
Chicken spermatocyte (a) and oocyte (b) after immunolocalization of SYCP3 (red), centromeric proteins (blue), and MLH1 (green). Arrows point to the synaptonemal complexes of the macrochromosomes identified by their lengths and centromeric indices. Arrowheads indicate MLH1 signals at ZW bivalent. Scale bar, 5 μm. (a From Malinovskaya et al. [2019], licensed under Creative Commons Attribution 4.0 License. b From Torgasheva et al. [2021], licensed under Creative Commons Attribution 4.0 License).
Fig. 32
Fig. 32
Immunolocalization of recombination and FISH mapping of single-copy sequences on synaptonemal complexes of the chicken. a Immunostained chicken oocyte showing the complete set of synaptonemal complexes labeled with anti-SMC3 and the crossovers detected with anti-MLH1. The 8 largest autosomal bivalents have a number next to the centromere signal (red protruding marks). The ZW pair has a single MLH1 focus located near the homologous end of the bivalent. Scale bar, 10 μm. b Localization of BAC clone 40N14 on the synaptonemal complex of GGA1 (SC1). The BAC insert is at 1.2 Mb from the sequence start. Scale bar, 1 μm. c Graph showing the distribution of distances from the end of SC1 to the FISH signal in 8 pachytene nuclei. (Data from del Priore and Pigozzi [2021]).
Fig. 33
Fig. 33
Recombination rates along GGA macrochromosomes 1 to 8. Each chromosome is divided in cells of 2.5 Mb. The recombination rates are represented by the different colours as indicated in the legend. The arrowheads point at the centromere positions calculated from the centromeric indexes in synaptonemal complex spreads.
Fig. 34
Fig. 34
MLH1 recombination maps of GGA1 and GGA5 integrated to physical positions. In both graphs the xaxis is the length of the chromosome in Mb from the sequence start on the short arm (p) to the end on the long arm (q) with cindicating the centromere. A schematic representation of the chromosomes is shown below. a The shaded area between the lines represents a chromosome region localized between 263 and 285 cM in a QTL analysis [Hansen et al., 2005]. The physical location of this region can be predicted from distribution of the cumulative cM distances (blue line). b The shaded area near the centromere spans over 8 Mb and contains multiple QTL for 2 myopathies [Lake et al., 2021]. The MLH1-cM map shows the recombination pattern in this segment.
Fig. 35
Fig. 35
Organisation of regions on chicken chromosome 16, as currently published. a Depiction of chromosome 16, based on analysis by FISH, radiation hybrids, genetics, southern blotting, and sequencing. B, B locus; GC, G+C-rich region of PO1 repeats; Y, Rfp-Y region; NOR, nucleolar organiser region; BLA, class II A gene; fB, factor B gene; ORs, olfactory receptor genes; SRCRs, scavenger receptor with cysteine repeat genes. Double-headed arrows indicate recombination frequencies between B and BLA, fB and Rfp-Y, and B and Rfp-Y. b Region of the B locus currently sequenced, including the BF-BL region, the TRIM region and the BG region. Genes represented by boxes. Rising and falling stripes indicate genes of the classical class I and class II presentation system, respectively; stippled indicate class II region genes; black indicates lectin-like genes and pseudogenes; horizontal stripes indicate TRIM family genes; vertical stripes indicate BG genes. Names of genes above indicate transcription from left to right, below indicate transcription from right to left; note the homologous genes in opposite transcriptional orientation in the BF-BL region but in the same transcriptional orientation in the BG region, strongly affecting the dynamics of evolution based on recombination. Figure from Kaufman [2021].
Fig. 36
Fig. 36
The basis for the PCR-NGS typing of the chicken MHC. Organisation of the BF-BL region and gene names from Kaufman et al. [1999b] (RING3is now known as BRD2); primers are designated by lab names. Figure from Martin [2021].
Fig. 37
Fig. 37
The chicken classical class I sequences mostly separate into 2 large clades (a), while classical class II B sequences are all mixed together in phylogenetic trees (b). BLB* indicates class II B sequences that could not easily be assigned to the BLB1or BLB2loci in the haplotypes examined. Figure from Martin [2021], derived from data available in 2020.
Fig. 38
Fig. 38
Sampling of global Gallusspp. diversity. The map shows the sampling locations for the 4,392 genomes from domestic chickens and congeneric jungle fowl species. To illustrate group size, commercial birds and European fancy breeds are also included on the map, although physical sampling location is not presumed to be important for these birds.
Fig. 39
Fig. 39
Processing pipeline. To ensure between-sample consistency, all samples have been re-processed from raw fastq reads. Reads underwent pre-processing and quality control before mapping to the latest version of the chicken genome (GRCg7b), variant calling, and generating a VCF.
Fig. 40
Fig. 40
Biobanking primordial germ cells (PGCs) and chimera chicken production at CTLGH/ILRI. PGCs are isolated from the germinal crescent of the blastoderm, from the circulating blood or from embryonic gonads at day 2.5 of their development (1), the isolated cells are immediately transferred into the freezing medium (2) and kept overnight in Mr Frosty before transfer for cryopreservation in liquid nitrogen (3). For use in the case of gonadal PGCs, the embryonic gonads removed from the liquid nitrogen are dissociated, characterized, and propagated if necessary (4) or directly injected into a 2-day-old recipient embryo for gonad re-colonization. The injected egg will be incubated up to day 21 to produce the chimeric chick (6) which may be very similar to the recipient breed. Depending on the level of gonad colonization by the donor PGCs, the mature chimeric chicken may display some phenotypic characteristics of the donor breed (7).
Fig. 41
Fig. 41
Protocols for the restoration of biobanked tropical poultry genetic resources and the potential dissemination of potential elite lines using chimeras (a−1) and gene edited surrogate host technology (a−2 and b).
Fig. 42
Fig. 42
Schematic illustration for future application of genome-edited poultry to industries. Genome editing in poultry can improve disease resistance and meat productivity. By targeting egg white protein genes, genome edited poultry can economically produce protein drugs with improved biological efficacy. When the reported genes are targeted to the Z chromosome, the male embryo can be screened out before hatching by detecting fluorescence during incubation.
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